Lower Limbs 1

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

This is an excellent list of key anatomical structures in the gluteal region. Here is a structured and detailed explanation of each item, organized by category.

Overview of the Gluteal Region

The gluteal region, commonly known as the buttock, is a critical anatomical area for locomotion and stability. It contains powerful muscles responsible for extending, abducting, and rotating the hip, as well as a dense network of major nerves and blood vessels that supply the lower limb and perineum.

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Muscles

The muscles are often divided into superficial and deep layers.

Superficial Muscles (Primary Extensors and Abductors)

• Gluteus Maximus Muscle: The largest and most superficial gluteal muscle.

  • Action: Powerful extensor of the thigh (e.g., rising from a sitting position, climbing stairs) and lateral rotator.

  • Innervation: Inferior Gluteal Nerve.

• Gluteus Medius Muscle: Lies deep to the gluteus maximus.

  • Action: Major abductor of the thigh; its anterior fibers also medially rotate the thigh. Crucial for stabilizing the pelvis during walking (e.g., preventing the opposite side of the pelvis from dropping).

  • Innervation: Superior Gluteal Nerve.

• Gluteus Minimus Muscle: The smallest and deepest of the three main gluteal muscles, located deep to the gluteus medius.

  • Action: Abducts and medially rotates the thigh. Works with the gluteus medius for pelvic stability.

  • Innervation: Superior Gluteal Nerve.

Deep Muscles (The "Deep Six" Lateral Rotators)

This group of six short muscles primarily act to laterally (externally) rotate the thigh. They are deeply placed and are crucial for understanding the relationships of nerves and vessels.

• Piriformis Muscle: The most superior and important landmark of the region. The Sciatic Nerve typically exits the pelvis by passing inferior to this muscle.

  • Action: Lateral rotator and abductor of the thigh.

• Superior Gemellus Muscle: Located immediately inferior to the piriformis.

• Inferior Gemellus Muscle: Located immediately superior to the quadratus femoris.

• Tendon of Obturator Internus Muscle: This muscle originates inside the pelvis, exits through the lesser sciatic foramen, and its tendon passes between the gemelli muscles. The gemelli muscles are often considered functional extensions of the obturator internus.

• Quadratus Femoris Muscle: The most inferior of the deep group. It is a strong lateral rotator and lies directly adjacent to the hip joint.

• Tendon of Obturator Externus Muscle: This muscle originates on the external side of the obturator foramen and passes deep to the quadratus femoris to insert on the femur. It is not always included in the classic "deep six" but is a lateral rotator.

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Nerves

The gluteal region contains some of the body's most important peripheral nerves.

• Superior Gluteal Nerve: Exits the pelvis above the piriformis muscle. It innervates the gluteus medius, gluteus minimus, and tensor fasciae latae muscles. Damage causes a characteristic "Trendelenburg gait."

• Inferior Gluteal Nerve: Exits the pelvis below the piriformis muscle. It exclusively innervates the gluteus maximus muscle. Damage results in weakened hip extension.

• Sciatic Nerve: The body's largest nerve. It exits the pelvis below the piriformis muscle and runs down the posterior thigh. It innervates most of the muscles in the leg and foot.

• Tibial Nerve: One of the two terminal branches of the sciatic nerve (usually arising in the lower thigh). It provides motor innervation to the posterior compartment of the leg and sole of the foot.

• Common Peroneal (Fibular) Nerve: The other terminal branch of the sciatic nerve. It is more lateral and susceptible to injury as it wraps around the fibular neck. It innervates the anterior and lateral compartments of the leg.

• Posterior Femoral Cutaneous Nerve: Exits below the piriformis. It does not supply muscles but provides sensory innervation to the skin of the buttock, posterior thigh, and popliteal fossa.

• Pudendal Nerve: Exits the pelvis below the piriformis but immediately re-enters the perineum through the lesser sciatic foramen. It is the primary nerve of the perineum, providing motor and sensory innervation to the external genitalia and muscles of the perineum.

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Vessels

• Superior Gluteal Vessels: The terminal branches of the internal iliac artery and vein. They exit the pelvis above the piriformis muscle alongside the superior gluteal nerve and are the major blood supply to the gluteal muscles.

• Inferior Gluteal Vessels: Branches of the internal iliac artery and vein. They exit the pelvis below the piriformis muscle, alongside the inferior gluteal nerve and sciatic nerve. They supply the deeper gluteal structures.

• Internal Pudendal Vessel: Exits the pelvis below the piriformis with the pudendal nerve and re-enters the perineum to supply the external genitalia and perineal structures.

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Other Structures

• Iliotibial (IT) Band of the Fascia Lata: A thick, fibrous band of connective tissue that runs down the lateral thigh. The gluteus maximus and tensor fasciae latae muscles insert into it, and it stabilizes the knee during movement.

• Gluteal Tuberosity of Femur: A bony ridge on the posterior surface of the proximal femur. It is the insertion point for the deep fibers of the gluteus maximus muscle.

Clinical Correlation: The Piriformis as a Landmark

The relationship of the Piriformis Muscle to the neurovascular structures is a key surgical and diagnostic landmark, often remembered by the mnemonic:

"Goats In Pools Are Goats In Pools"

• Gluteus medius & minimus, Inferior gluteal vessels & nerve, Pudendal nerve & internal pudendal vessels, Posterior femoral cutaneous nerve, Sciatic nerve, Inferior gluteal vessels & nerve (again), Pudendal nerve & internal pudendal vessels (again).

A more precise and simpler way to remember the major structures is:

• Above Piriformis: Superior Gluteal Nerve & Vessels.

• Below Piriformis (in order, from medial to lateral):

  1. Pudendal Nerve & Internal Pudendal Vessels

  2. Nerve to Obturator Internus

  3. Posterior Femoral Cutaneous Nerve

  4. Inferior Gluteal Nerve & Vessels

  5. Sciatic Nerve

  6. Nerve to Quadratus Femoris

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Gluteus Maximus muscle.

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Gluteus Maximus Muscle1. Etymology (Word Origin)

The name "Gluteus Maximus" is derived directly from Latin and Greek roots:

• Gluteus: From the Greek word "gloutos" (γλουτός), which simply means "buttock" or "rump."

• Maximus: From Latin, meaning "greatest" or "largest."

Therefore, Gluteus Maximus literally translates to "the largest muscle of the buttock," which is an accurate description, as it is the most massive and superficial muscle in that region.

2. Function

The gluteus maximus is a powerful muscle with several key actions on the hip joint. Its functions can be broken down as follows:

A. Primary Actions:

1. Extension of the Thigh: This is its most powerful and primary action. The gluteus maximus is the main extensor of the hip, bringing the thigh backward in the sagittal plane.

   • Examples in daily life:

     • Rising from a seated or squatting position.

     • Walking up a steep hill or climbing stairs.

     • The powerful upward thrust during running, jumping, and cycling.

2. Lateral (External) Rotation of the Thigh: It powerfully rotates the extended thigh away from the midline of the body.

   • Example: The action of swinging your leg out to the side while walking.

B. Secondary Actions (depending on the part of the muscle used):

• Upper Fibers: Can aid in Abduction (moving the thigh away from the midline).

• Lower Fibers: Can aid in Adduction (moving the thigh toward the midline).

C. Stabilizing Role:

• Iliotibial (IT) Band Stabilization: A large portion of the gluteus maximus inserts into the Iliotibial (IT) Band, a thick band of fascia that runs down the lateral thigh. By tensing this band, the muscle plays a crucial role in:

  • Stabilizing the knee joint in extension (especially when standing).

  • Stabilizing the hip joint.

  • Maintaining upright posture by preventing the trunk from flexing forward at the hips.

D. Clinical Significance:

• "Dead Butt Syndrome" (Gluteus Medius/Maximus Tendinopathy): Weakness or inhibition of the gluteus maximus (and medius) is common in sedentary individuals. This can lead to compensatory patterns, placing excessive stress on the lower back, hamstrings, and knees, contributing to pain and injury.

• Injection Site: The upper outer quadrant of the gluteal region is a common site for intramuscular injections, specifically chosen to avoid the Sciatic Nerve and Inferior Gluteal Nerve and vessels, which lie in the lower medial quadrant.

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Summary

Feature	Description
Etymology	"Gluteus" (Gr. buttock) + "Maximus" (L. largest) = "Largest muscle of the buttock"
Primary Function	Powerful extension and lateral rotation of the thigh at the hip joint.
Key Role	Essential for upright posture, locomotion (especially climbing and running), and stabilizing the hip and knee.
Innervation	Inferior Gluteal Nerve (L5, S1, S2)

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Iliotibial Band (IT Band).

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Iliotibial Band (Tract) of the Fascia Lata1. Etymology (Word Origin)

The name is a direct description of its anatomical attachments and structure:

• Ilio-: Refers to the Ilium, the large, wing-like bone of the pelvis.

• Tibial: Refers to the Tibia, the larger of the two bones in the lower leg (shin bone).

• Band: Describes its structure—a long, strong, fibrous band.

• Fascia Lata: From Latin, meaning "wide fascia." This is the deep fascia (a sheet of connective tissue) that envelops the entire thigh.

Therefore, Iliotibial Band of the Fascia Lata literally translates to "the band running from the ilium to the tibia, which is part of the wide fascia of the thigh."

2. Function

The IT Band is not a muscle but a passive structure of thick, fibrous connective tissue. Its functions are primarily mechanical and stabilizing.

A. Primary Stabilizing Functions:

1. Lateral Knee Stabilization: This is one of its most critical roles. The IT band passes over the lateral side of the knee joint and inserts on the tibia. It acts as a dynamic stabilizer to prevent excessive varus (bow-legged) stress on the knee.

   • Mechanism: It tenses during leg movement, particularly when the knee is bent at around 20-30 degrees, to keep the knee stable.

2. Hip Stabilization: The IT band provides an essential attachment point for two major hip muscles:

   • Tensor Fasciae Latae (TFL): Inserts directly into the IT band.

   • Gluteus Maximus: A significant portion of its lower fibers also insert into the IT band.

   • By serving as a "distal tendon" for these muscles, the IT band translates their force down the leg, aiding in hip abduction (moving the leg away from the body) and hip extension.

3. Upright Posture and Gait: The tension maintained in the IT band helps maintain an extended knee while standing, reducing the muscular effort required from the quadriceps. During walking and running, it stores and releases elastic energy, contributing to efficient locomotion.

B. Clinical Significance: Iliotibial Band Syndrome (ITBS)

• What it is: This is a common overuse injury, often referred to as "runner's knee." It is one of the most frequent causes of lateral knee pain in athletes.

• Cause: It is typically caused by repetitive friction of the IT band sliding over a bony prominence on the outside of the knee (the lateral femoral epicondyle) as the knee bends and straightens.

• Symptoms: A sharp or burning pain on the outside of the knee, especially during activities like running or cycling.

• Contributing Factors: Weak hip muscles (gluteus medius/maximus), tightness in the IT band or TFL, and poor biomechanics during exercise.

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Summary

Feature	Description
Etymology	"Ilio-" (Ilium) + "Tibial" (Tibia) + "Band" + "Fascia Lata" (wide fascia) = The band from the pelvis to the shin bone.
Primary Function	Stabilization of the lateral knee and hip. It acts as a passive tension band.
Key Role	Serves as a distal attachment for the Tensor Fasciae Latae and Gluteus Maximus, translating their force to stabilize the lower limb during standing, walking, and running.
Clinical Note	Iliotibial Band Syndrome (ITBS) is a common overuse injury causing pain on the outside of the knee.

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Gluteal Tuberosity of the femur.

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Gluteal Tuberosity of the Femur1. Etymology (Word Origin)

The name is a direct anatomical description of its location and purpose:

• Gluteal: Pertaining to the gluteal region, or the buttocks. Specifically, it refers to the Gluteus Maximus muscle.

• Tuberosity: From the Latin tuber, meaning "a swelling" or "lump." In anatomy, a tuberosity is a large, rounded, and usually roughened bony prominence that serves as a point of attachment for a tendon or ligament.

Therefore, Gluteal Tuberosity literally translates to "the rough, raised impression on the femur for the gluteal muscle."

2. Function

The gluteal tuberosity has one primary, crucial function:

A. Primary Function: Tendon Attachment Site

The gluteal tuberosity serves as the primary insertion point for the deep fibers of the Gluteus Maximus muscle.

• Mechanism: The powerful tendon of the gluteus maximus inserts onto this roughened area of bone. The roughness is essential as it provides a strong, grippable surface for the tendon's collagen fibers to anchor into the bone (via Sharpey's fibers), resisting the immense pulling forces generated by the muscle.

• Force Transfer: When the gluteus maximus contracts, it pulls on the gluteal tuberosity. This pull is what creates the actions of:

  • Thigh Extension: The main action, powered by this insertion.

  • Lateral (External) Rotation of the Thigh.

B. Anatomical Significance and Relationship to the Linea Aspera

The gluteal tuberosity is not an isolated bump but is more accurately described as a vertical ridge located on the upper part of the Linea Aspera on the posterior side of the femur.

• Linea Aspera: Meaning "rough line," this is a prominent longitudinal ridge or crest that runs along the back of the femoral shaft. It is a major site for muscle attachments (like the adductors) and is where the medial and lateral lips of the femur converge.

• The gluteal tuberosity represents the superior continuation of the lateral lip of the linea aspera. In some individuals, it is a well-defined ridge, while in others, it is a less distinct, roughened area.

C. Clinical Correlation

• Avulsion Fracture: While rare due to the strength of the bone and tendon, an extremely powerful and sudden contraction of the gluteus maximus could, in theory, avulse (tear away) a small fragment of bone at the gluteal tuberosity. This is more common in adolescent athletes where the growth plates are not fully fused.

• Surgical Landmark: The linea aspera, and by extension the gluteal tuberosity region, serves as an important landmark for surgeons during femoral (thigh bone) procedures.

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Summary

Feature	Description
Etymology	"Gluteal" (of the buttock) + "Tuberosity" (roughened swelling) = The roughened impression for the gluteus maximus muscle.
Primary Function	Serves as the bony insertion point for the deep fibers of the Gluteus Maximus tendon.
Key Role	Anchors the body's most powerful hip extensor, allowing for the transfer of force from muscle to bone, enabling powerful movements like rising from a chair, climbing stairs, and running.
Anatomic Location	A vertical ridge located on the proximal (upper) part of the Linea Aspera on the posterior side of the femur.

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Gluteus Medius muscle.

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Gluteus Medius Muscle1. Etymology (Word Origin)

The name "Gluteus Medius" follows the same logical structure as the other gluteal muscles, derived from Latin and Greek:

• Gluteus: From the Greek word "gloutos" (γλουτός), meaning "buttock" or "rump."

• Medius: From Latin, meaning "middle."

Therefore, Gluteus Medius literally translates to "the middle gluteal muscle," which accurately describes its anatomical position, lying deep to the Gluteus Maximus and superficial to the Gluteus Minimus.

2. Function

The gluteus medius is a critical muscle for locomotion and pelvic stability. Its functions are primarily focused on hip abduction and stabilization.

A. Primary Actions:

1. Abduction of the Thigh: It is a primary abductor of the hip, moving the thigh away from the midline of the body.

2. Pelvic Stabilization (Most Critical Function): This is the gluteus medius's most important role during walking and running. When you stand on one leg (the "stance leg"), the gluteus medius on that side contracts powerfully.

   • Action: It prevents the opposite side of the pelvis from dropping. This is essential for maintaining a level pelvis during the single-leg support phase of gait.

B. Secondary Actions (based on fiber orientation):

The muscle's fan-like shape means different parts of it can produce different movements:

• Anterior Fibers: Contract to produce Medial (Internal) Rotation and Flexion of the thigh.

• Posterior Fibers: Assist in Lateral (External) Rotation and Extension of the thigh.

C. Clinical Significance: The Trendelenburg Sign

• What it is: Weakness or paralysis of the gluteus medius (e.g., due to injury to the Superior Gluteal Nerve, polio, or after hip surgery) leads to a classic clinical finding.

• The Test: When a patient stands on the weak leg, the pelvis on the opposite side will droop or sag.

• The Gait: This results in a "Trendelenburg Gait." To compensate, the patient lurches their torso over the weak stance leg during walking to balance the center of gravity. It is often described as a "waddling" gait.

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Summary

Feature	Description
Etymology	"Gluteus" (Gr. buttock) + "Medius" (L. middle) = "The middle muscle of the buttock"
Primary Function	Abduction of the thigh and stabilization of the pelvis during single-leg stance (e.g., walking).
Key Role	Prevents pelvic drop on the unsupported side. It is fundamental for a normal, stable gait.
Innervation	Superior Gluteal Nerve (L4, L5, S1)
Clinical Note	Weakness causes a positive Trendelenburg Sign and an abnormal Trendelenburg Gait.

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Gluteus Minimus muscle.

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Gluteus Minimus Muscle1. Etymology (Word Origin)

The name "Gluteus Minimus" follows the same logical nomenclature as the other gluteal muscles, derived from Latin and Greek:

• Gluteus: From the Greek word "gloutos" (γλουτός), meaning "buttock" or "rump."

• Minimus: From Latin, meaning "smallest" or "least."

Therefore, Gluteus Minimus literally translates to "the smallest gluteal muscle," which accurately describes it as the smallest and deepest of the three primary gluteal muscles (Maximus, Medius, Minimus).

2. Function

The gluteus minimus works in close concert with the gluteus medius, and their functions are nearly identical. It is a key stabilizer of the hip and pelvis.

A. Primary Actions:

1. Abduction of the Thigh: It is a primary abductor of the hip, working with the gluteus medius to move the thigh away from the midline of the body.

2. Pelvic Stabilization (Critical Function): Like the gluteus medius, its most important role is to stabilize the pelvis during single-leg weight-bearing activities, such as walking or running.

   • Action: When you stand on one leg, the gluteus minimus (on that side) contracts to prevent the opposite side of the pelvis from dropping. This maintains a level pelvis for efficient gait.

B. Secondary Actions (based on fiber orientation):

The muscle is fan-shaped, and its anterior and posterior fibers have different lines of pull:

• Anterior Fibers: These are the primary actors for Medial (Internal) Rotation of the thigh. They may also assist in slight flexion.

• Posterior Fibers: Assist the gluteus medius in Lateral (External) Rotation and stabilization.

C. Clinical Significance

• Trendelenburg Gait: Weakness or dysfunction of the gluteus minimus (and medius) is a primary cause of the Trendelenburg sign and gait. This occurs when the pelvis sags on the unsupported side during single-leg stance due to inadequate stabilization from the weight-bearing side's gluteal muscles.

• Innervation: It is innervated by the Superior Gluteal Nerve (L4, L5, S1). An injury to this nerve will paralyze both the gluteus medius and minimus, leading to a significant loss of pelvic stability.

• Referred Pain: Trigger points or pathology in the gluteus minimus are a very common source of lateral hip pain, which can often be mistaken for trochanteric bursitis.

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Summary

Feature	Description
Etymology	"Gluteus" (Gr. buttock) + "Minimus" (L. smallest) = "The smallest muscle of the buttock"
Primary Function	Abduction of the thigh and stabilization of the pelvis during single-leg stance.
Key Role	Works synergistically with the Gluteus Medius to prevent pelvic drop. Its anterior fibers are key medial rotators of the hip.
Innervation	Superior Gluteal Nerve (L4, L5, S1)
Clinical Note	Weakness contributes to a Trendelenburg Gait. It is a common source of lateral hip pain.

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Piriformis muscle.

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Piriformis Muscle1. Etymology (Word Origin)

The name "Piriformis" is derived from Latin and provides a perfect description of its shape:

• Piri-: From the Latin pirum, meaning "pear."

• -formis: From the Latin formis, meaning "shape" or "form."

Therefore, Piriformis literally translates to "pear-shaped muscle," which accurately describes its morphology.

2. Function

The piriformis is the most superior and important landmark of the deep gluteal muscles (the lateral rotators). Its functions are primarily rotational and stabilizing.

A. Primary Action:

• Lateral (External) Rotation of the Thigh: This is its primary action when the hip is in a neutral or extended position. It rotates the femur outward, turning the foot and knee away from the midline of the body.

B. Secondary Actions (depending on hip position):

• Hip Abduction: When the hip is flexed to 90 degrees or more, the line of pull of the piriformis changes, and it becomes an abductor of the thigh (moving the thigh away from the midline).

• Hip Stabilizer: As part of the deep rotator group, it helps to stabilize the head of the femur within the acetabulum (hip socket), especially during locomotion.

C. Clinical Significance: The Piriformis as a Landmark and Source of Pathology

The piriformis is far more clinically significant for the structures that pass by it than for its own action.

1. Neurovascular Landmark: The piriformis is the key anatomical landmark for the gluteal region. It is used to define the passage of major nerves and vessels from the pelvis (the greater sciatic foramen) into the gluteal region:

   • Superior to Piriformis: Superior Gluteal Nerve & Vessels.

   • Inferior to Piriformis (mnemonic "POPSIQQ" or similar): Pudendal nerve, Nerve to Obturator Internus, Posterior Femoral Cutaneous Nerve, Sciatic Nerve, Inferior Gluteal Nerve & Vessels, Nerve to Quadratus Femoris.

2. Piriformis Syndrome:

   • What it is: A condition where the piriformis muscle spasms, hypertrophies, or becomes tight, potentially compressing or irritating the sciatic nerve, which most commonly runs inferior to the muscle.

   • Symptoms: Pain, tingling, or numbness deep in the buttock that can radiate down the back of the leg (sciatica-like pain).

   • Anatomical Variation: In a small percentage of the population, the sciatic nerve (or a portion of it) pierces through the piriformis muscle, which may predispose them to this condition.

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Summary

Feature	Description
Etymology	"Piri-" (L. pear) + "-formis" (L. shape) = "Pear-shaped muscle."
Primary Function	Lateral (External) Rotation of the thigh at the hip joint.
Key Role	Serves as the critical anatomical landmark for neurovascular structures exiting the pelvis. Stabilizes the hip joint.
Innervation	Nerve to Piriformis (S1, S2)
Clinical Note	Piriformis Syndrome is a potential cause of sciatica-like pain due to sciatic nerve compression/irritation.

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Superior Gluteal Nerve.

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Superior Gluteal Nerve1. Etymology (Word Origin)

The name is a direct description of its anatomical position and target:

• Superior: From Latin, meaning "upper" or "above."

• Gluteal: Pertaining to the gluteal region (buttocks).

• Nerve: From the Greek "neuron" (νεῦρον), meaning tendon, sinew, or later, nerve.

Therefore, Superior Gluteal Nerve literally translates to "the upper nerve of the buttock." This distinguishes it from the Inferior Gluteal Nerve ("the lower nerve of the buttock").

2. Function

The Superior Gluteal Nerve is a motor nerve, meaning its primary role is to control muscles. It is essential for stable walking and pelvic control.

A. Primary Function: Motor Innervation

The superior gluteal nerve is responsible for supplying three key muscles involved in hip abduction and medial rotation:

1. Gluteus Medius Muscle

2. Gluteus Minimus Muscle

3. Tensor Fasciae Latae (TFL) Muscle

B. Resulting Actions and Clinical Significance

By innervating these muscles, the superior gluteal nerve enables two critical functions:

1. Hip Abduction: All three muscles it supplies are primary abductors, moving the leg away from the midline.

2. Pelvic Stabilization (Most Critical Function): This is the nerve's most vital role.

   • Mechanism: When you stand on one leg (during the "stance phase" of gait), the gluteus medius and minimus on that side contract powerfully.

   • Action: This contraction prevents the opposite side of the pelvis from dropping. This is essential for maintaining a level pelvis and a smooth, efficient walking pattern.

C. Clinical Correlation: Injury and the Trendelenburg Sign

• Cause of Injury: The superior gluteal nerve can be damaged by:

  • Intramuscular injections given in the wrong quadrant of the buttock.

  • Pelvic fractures or hip surgery.

  • Compression by tumors or during prolonged sitting.

• The Trendelenburg Sign:

  • What it is: A classic physical exam finding indicating weakness of the gluteus medius and minimus due to superior gluteal nerve dysfunction.

  • The Test: When a patient stands on the leg with the weak gluteal muscles (the affected side), the pelvis on the opposite side will droop or sag.

  • The Gait: This results in a "Trendelenburg Gait" or "gluteus medius limp." To compensate, the patient lurches their torso over the weak stance leg during walking to shift their center of gravity and prevent falling.

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Summary

Feature	Description
Etymology	"Superior" (L. upper) + "Gluteal" (of the buttock) + "Nerve" = "The upper nerve of the buttock."
Primary Function	Motor innervation to the Gluteus Medius, Gluteus Minimus, and Tensor Fasciae Latae muscles.
Key Role	Enables hip abduction and, most critically, stabilization of the pelvis during walking. Prevents pelvic drop on the unsupported side.
Nerve Roots	L4, L5, S1
Clinical Note	Damage causes weakness in hip abduction and a positive Trendelenburg Sign, leading to a characteristic Trendelenburg Gait.

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Superior Gluteal Vessels.

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Superior Gluteal Vessels1. Etymology (Word Origin)

The name is a direct description of their anatomical origin and path:

• Superior: From Latin, meaning "upper" or "above."

• Gluteal: Pertaining to the gluteal region (the buttocks).

• Vessels: A collective term for arteries and veins.

Therefore, Superior Gluteal Vessels literally translates to "the upper blood vessels of the buttock." This distinguishes them from the Inferior Gluteal Vessels ("the lower blood vessels of the buttock").

2. Function

The Superior Gluteal Vessels are the major vascular supply to the muscles and structures of the gluteal region.

A. Primary Function: Vascular Supply

1. Artery:

   • The Superior Gluteal Artery is the largest branch of the internal iliac artery. It is the primary and dominant blood supply to the gluteal region.

   • Structures Supplied:

     • Muscles: Gluteus Maximus, Gluteus Medius, Gluteus Minimus, Tensor Fasciae Latae, and the deep rotator muscles (e.g., Piriformis).

     • Bone: It contributes to the blood supply of the hip bone (ilium).

     • Skin: It provides cutaneous branches to the skin over the superior buttock.

2. Vein:

   • The Superior Gluteal Vein follows the course of the artery in reverse.

   • Function: It drains deoxygenated blood from the same structures supplied by the artery.

   • Termination: It empties into the internal iliac vein, which returns blood to the systemic circulation.

B. Anatomical Course: A Key Landmark

The relationship of these vessels to the Piriformis muscle is a critical surgical and anatomical landmark.

• They exit the pelvis through the greater sciatic foramen, superior to the Piriformis muscle.

• They run alongside the Superior Gluteal Nerve.

This relationship is often remembered with the mnemonic for structures exiting the greater sciatic foramen:

• Above Piriformis: Superior Gluteal Nerve & Vessels.

• Below Piriformis: Everything else (Pudendal nerve, Sciatic nerve, Inferior gluteal nerve/vessels, etc.).

C. Clinical Significance

• Surgical Hazard: Due to their deep location and proximity to bone and major nerves, the superior gluteal vessels are at risk during posterior approaches to the hip joint and pelvis. Damage can lead to significant, deep bleeding that is difficult to control.

• Intramuscular Injection Site: The "upper outer quadrant" of the buttock is the safe zone for injections precisely to avoid injury to the Superior and Inferior Gluteal vessels and the Sciatic Nerve, which are located in the medial and lower portions.

• Collateral Circulation: The superior gluteal artery anastomoses (connects) with branches of the inferior gluteal artery, lateral femoral circumflex artery, and the medial femoral circumflex artery. This network provides a collateral blood supply to the hip region, which can become vital if one vessel is blocked.

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Summary

Feature	Description
Etymology	"Superior" (L. upper) + "Gluteal" (of the buttock) + "Vessels" = "The upper blood vessels of the buttock."
Primary Function	The Superior Gluteal Artery is the main blood supply to the gluteal muscles and skin. The Superior Gluteal Vein drains blood from the same area.
Key Role	Essential for oxygenation and nutrition of all major gluteal muscles. Their course superior to the Piriformis muscle is a fundamental anatomical landmark.
Origin/End	Artery: Branch of the Internal Iliac Artery. Vein: Drains into the Internal Iliac Vein.
Clinical Note	At risk during posterior hip surgery. Their location defines the safe zone for intramuscular injections.

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Inferior Gluteal Nerve.

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Inferior Gluteal Nerve1. Etymology (Word Origin)

The name is a direct description of its anatomical position and target:

• Inferior: From Latin, meaning "lower" or "below."

• Gluteal: Pertaining to the gluteal region (the buttocks).

• Nerve: From the Greek "neuron" (νεῦρον).

Therefore, Inferior Gluteal Nerve literally translates to "the lower nerve of the buttock." This distinguishes it from the Superior Gluteal Nerve ("the upper nerve of the buttock").

2. Function

The Inferior Gluteal Nerve is a pure motor nerve, meaning its sole function is to control muscle movement. It does not carry sensory information.

A. Primary and Exclusive Function: Motor Innervation

The inferior gluteal nerve is responsible for supplying the Gluteus Maximus muscle.

• It is the only nerve that innervates this muscle.

• There is no redundant or shared innervation from other nerves.

B. Resulting Actions

By innervating the gluteus maximus, the inferior gluteal nerve enables this muscle's powerful actions:

1. Extension of the Hip: This is the primary action. It is essential for:

   • Rising from a seated or squatting position.

   • Climbing stairs or walking up an incline.

   • The powerful upward thrust during running and jumping.

2. Lateral (External) Rotation of the Thigh: The gluteus maximus is a powerful lateral rotator of the hip.

3. Stabilization: It helps stabilize the extended knee joint via its insertion into the Iliotibial (IT) Band and stabilizes the trunk on the thigh during upright posture.

C. Clinical Correlation: Injury and Gait Disturbance

• Cause of Injury: The inferior gluteal nerve can be damaged by:

  • Improper intramuscular injections in the buttock (a key reason the upper outer quadrant is the safe zone).

  • Posterior hip dislocations or fractures.

  • Compression by tumors or during surgical procedures.

• Consequences of Injury:

  • Paralysis/Weakness of Gluteus Maximus: Since the nerve is the sole supplier, damage results in significant weakness or complete paralysis of the muscle.

  • Gait Abnormality: The most noticeable effect is difficulty with hip extension. Patients have trouble:

    • Rising from a chair without using their arms to push off.

    • Climbing stairs, which requires powerful hip extension.

    • Lurching Gait: During the "toe-off" phase of walking, the patient often lurches their trunk backward over the stance leg to passively maintain hip extension, as the gluteus maximus cannot actively perform this action.

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Summary

Feature	Description
Etymology	"Inferior" (L. lower) + "Gluteal" (of the buttock) + "Nerve" = "The lower nerve of the buttock."
Primary Function	Exclusive motor innervation to the Gluteus Maximus muscle.
Key Role	Enables powerful hip extension and lateral rotation. Essential for activities like rising from a chair, climbing, and running.
Nerve Roots	L5, S1, S2
Clinical Note	Damage causes profound weakness in hip extension, leading to a characteristic difficulty in rising from a seated position and a lurching gait.

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Inferior Gluteal Vessels.

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Inferior Gluteal Vessels1. Etymology (Word Origin)

The name is a direct description of their anatomical origin and path:

• Inferior: From Latin, meaning "lower" or "below."

• Gluteal: Pertaining to the gluteal region (the buttocks).

• Vessels: A collective term for arteries and veins.

Therefore, Inferior Gluteal Vessels literally translates to "the lower blood vessels of the buttock." This distinguishes them from the Superior Gluteal Vessels ("the upper blood vessels of the buttock").

2. Function

The Inferior Gluteal Vessels are a major vascular pedicle for the gluteal region, supplying key structures and participating in important anatomical anastomoses.

A. Primary Function: Vascular Supply

1. Artery:

   • The Inferior Gluteal Artery is a terminal branch of the anterior division of the internal iliac artery.

   • Structures Supplied:

     • Muscles: The primary blood supply to the Gluteus Maximus. It also supplies other muscles in the area, including the other lateral rotators (like the quadratus femoris), the upper parts of the hamstrings (semitendinosus, semimembranosus, biceps femoris), and part of the hip adductor magnus.

     • Other Structures: It contributes to the blood supply of the hip joint and gives off a crucial artery to the sciatic nerve (arteria comitans nervi ischiadici).

     • Anastomoses: It forms important collateral connections, primarily with the Superior Gluteal Artery and the Medial Femoral Circumflex Artery.

2. Vein:

   • The Inferior Gluteal Vein follows the course of the artery in reverse.

   • Function: It drains deoxygenated blood from the same structures supplied by the artery, most notably the gluteus maximus and the posterior thigh.

   • Termination: It empties into the internal iliac vein.

B. Anatomical Course: A Key Landmark

The relationship of these vessels to the Piriformis muscle is a critical surgical and anatomical landmark.

• They exit the pelvis through the greater sciatic foramen, inferior to the Piriformis muscle.

• They run in close association with other major neurovascular structures, including the Sciatic Nerve, Pudendal Nerve, and Inferior Gluteal Nerve.

This relationship is the reason the upper outer quadrant of the buttock is the safe zone for intramuscular injections—to avoid damaging these deeply placed vessels and nerves.

C. Clinical Significance

• Surgical Hazard: Similar to the superior vessels, the inferior gluteal artery is at risk during posterior approaches to the hip and pelvis. Its location deep to the gluteus maximus makes it vulnerable to injury.

• Cruciate Anastomosis: The inferior gluteal artery is a key participant in the "cruciate anastomosis" around the hip joint. This is a network of arteries (including the medial/lateral femoral circumflex arteries and the first perforating artery) that provides a vital collateral circulation. If the femoral artery is blocked, this anastomosis can help deliver blood to the lower limb.

• Intramuscular Injection Site: Knowledge of its location is essential to avoid intra-arterial injection, which can cause severe tissue damage and necrosis.

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Summary

Feature	Description
Etymology	"Inferior" (L. lower) + "Gluteal" (of the buttock) + "Vessels" = "The lower blood vessels of the buttock."
Primary Function	The Inferior Gluteal Artery is the main blood supply to the Gluteus Maximus and contributes to the posterior thigh. The Inferior Gluteal Vein drains blood from the same area.
Key Role	Vital for oxygenation of the gluteus maximus. A key component of the cruciate anastomosis, providing a collateral blood pathway around the hip.
Origin/End	Artery: Branch of the Internal Iliac Artery. Vein: Drains into the Internal Iliac Vein.
Clinical Note	At risk during posterior hip surgery. Its location inferior to the piriformis defines the danger zone for intramuscular injections.

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Sciatic Nerve, including a correction for the typo in "function."

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Sciatic Nerve1. Etymology (Word Origin)

The name "Sciatic" has a long history, tracing back to ancient Greek:

• Sciatic: Derived from the Late Latin sciaticus, which came from the Greek ischiadikos (ἰσχιαδικός)*.

• The Greek root is ischion (ἰσχίον)**, which means "hip" or "hip joint."

Therefore, Sciatic Nerve literally means "the nerve of the hip," which is fitting given its path from the lower spine, through the hip/gluteal region, and down the leg.

2. Function

The sciatic nerve is the longest and thickest nerve in the human body, approximately the width of a finger. It is actually a bundle of two major nerves wrapped in a common sheath: the Tibial Nerve and the Common Peroneal (Fibular) Nerve. It is a mixed nerve, containing both motor and sensory fibers.

A. Motor Innervation (Primary Function)

The sciatic nerve provides motor control to the muscles of the posterior thigh, leg, and foot. Its two components have distinct roles:

• Tibial Nerve Division: Innervates muscles in the:

  • Posterior Thigh: The hamstrings (except the short head of biceps femoris) and the hamstring part of adductor magnus.

  • Posterior Leg: The calf muscles (gastrocnemius, soleus, etc.) and deep flexors of the foot.

  • Sole of the Foot: All the small intrinsic muscles.

• Common Peroneal (Fibular) Nerve Division: Innervates muscles in the:

  • Anterior Leg: The muscles that dorsiflex the ankle and extend the toes.

  • Lateral Leg: The muscles that evert the foot.

B. Sensory Innervation

The sciatic nerve provides sensation to a large area of the lower limb:

• It does not typically provide sensation to the gluteal region itself (that's the job of the posterior femoral cutaneous nerve).

• It supplies sensation to the skin of most of the leg (except the medial side) and the entire foot.

C. Clinical Significance: Sciatica

• What it is: "Sciatica" is not a diagnosis itself, but a term for symptoms caused by irritation or compression of the sciatic nerve.

• Symptoms: The classic symptom is pain that radiates from the lower back, through the buttock, and down the back of the leg, often following the nerve's path. It can be accompanied by tingling, numbness, or muscle weakness in the leg or foot.

• Common Causes: A herniated lumbar disc pressing on one of the nerve roots (L4-S3) that form the sciatic nerve is the most common cause. Piriformis syndrome is another potential cause.

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Summary

Feature	Description
Etymology	From Gr. "ischion" (hip) → "the nerve of the hip."
Primary Function	Major motor and sensory nerve to the posterior thigh, leg, and foot. It is the primary nerve for the lower limb.
Key Role	Motor: Enables knee flexion (hamstrings), ankle movement (plantarflexion, dorsiflexion), and foot function. Sensory: Provides feeling to most of the leg and foot.
Nerve Roots	L4, L5, S1, S2, S3 (It is formed from the lumbosacral plexus).
Clinical Note	Compression or irritation causes Sciatica, characterized by radiating pain down the leg.

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Tibial Nerve.

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Tibial Nerve1. Etymology (Word Origin)

The name "Tibial" is a straightforward anatomical reference:

• Tibial: Pertaining to the Tibia, the larger of the two bones in the lower leg (the shin bone).

• Nerve: From the Greek "neuron" (νεῦρον).

Therefore, Tibial Nerve literally translates to "the nerve of the shin bone," which describes its path as it runs down the leg adjacent to the tibia.

2. Function

The Tibial Nerve is one of the two terminal branches of the Sciatic Nerve (the other being the Common Peroneal Nerve). It is a mixed nerve, containing both motor and sensory fibers, and is the larger of the two branches.

A. Motor Innervation (Primary Function)

The tibial nerve is the primary motor nerve for the posterior compartment of the leg and the sole of the foot. It provides the "power" for pushing off the ground.

• In the Posterior Thigh: It innervates most of the hamstring muscles (semitendinosus, semimembranosus, and the long head of biceps femoris) and the hamstring part of the adductor magnus.

• In the Posterior Leg (Calf): It innervates the superficial and deep calf muscles:

  • Superficial Group: Gastrocnemius, Soleus, and Plantaris (prime movers for plantarflexion - pointing the foot downward).

  • Deep Group: Popliteus, Tibialis Posterior, Flexor Digitorum Longus, Flexor Hallucis Longus (responsible for inversion of the foot and curling the toes).

• In the Sole of the Foot: Its terminal branch, the Medial and Lateral Plantar Nerves, innervates all the small intrinsic muscles of the foot that support the foot's arches and allow for fine motor control of the toes.

B. Sensory Innervation

The tibial nerve provides sensation to:

• The skin on the sole of the foot (via the Medial and Lateral Plantar Nerves).

• The heel (via the Medial Calcaneal Branches).

C. Clinical Significance

• Tarsal Tunnel Syndrome: Analogous to carpal tunnel syndrome in the wrist, this condition involves compression of the tibial nerve as it passes behind the medial malleolus (the inner ankle bone) within a fibrous tunnel called the tarsal tunnel. Symptoms include pain, tingling, and numbness in the sole of the foot.

• Injury Impact: Damage to the tibial nerve results in a significant loss of function:

  • Motor: Weakened or paralyzed plantarflexion and toe flexion, leading to an inability to stand on tiptoes and a slapping gait. The foot may assume a "clawfoot" appearance due to unopposed action of the dorsiflexors.

  • Sensory: Loss of sensation on the sole of the foot, which can be dangerous as it makes a person unable to feel injuries or foreign objects.

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Summary

Feature	Description
Etymology	"Tibial" (of the shin bone) + "Nerve" = "The nerve related to the tibia."
Primary Function	Major motor nerve to the posterior thigh (hamstrings), posterior leg (calf), and sole of the foot. Provides sensation to the sole.
Key Role	Enables plantarflexion (walking, running, jumping), inversion of the foot, and toe flexion. Essential for the push-off phase of gait.
Nerve Roots	L4, L5, S1, S2, S3 (as part of the sciatic nerve).
Clinical Note	Compression causes Tarsal Tunnel Syndrome. Injury leads to a loss of the ability to push off with the foot and sensory loss on the sole.

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Common Peroneal Nerve, including an explanation of its alternative name.

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Common Peroneal (Fibular) Nerve1. Etymology (Word Origin)

The name of this nerve has two versions, reflecting a modern shift in anatomical terminology:

• Common Peroneal:

  • Peroneal: Derived from the Greek word "perone" (περόνη), meaning "pin" or "brooch." It was historically used to refer to the fibula, the thinner bone of the lower leg, which was thought to resemble a pin.

  • Therefore, "Common Peroneal" means "the common nerve of the fibula."

• Common Fibular:

  • Fibular: This is the modern, preferred term. It is derived directly from "Fibula," the Latin word for a clasp or pin, which is the name of the bone itself.

  • Therefore, "Common Fibular" means the same thing but uses the direct name of the bone. "Fibular" is now the Terminologia Anatomica standard.

The "Common" in its name indicates that it is a short trunk that will divide into two terminal branches: the Superficial Fibular Nerve and the Deep Fibular Nerve.

2. Function

The Common Peroneal (Fibular) Nerve is the smaller of the two terminal branches of the Sciatic Nerve (the other being the Tibial Nerve). It is a mixed nerve, but its motor function is most clinically significant.

A. Motor Innervation (Primary Function)

After winding around the neck of the fibula, it divides into two main branches that control the muscles of the anterior and lateral compartments of the leg:

• Deep Fibular (Peroneal) Nerve: Innervates the muscles in the anterior compartment of the leg.

  • Muscles: Tibialis Anterior, Extensor Digitorum Longus, Extensor Hallucis Longus, and Peroneus Tertius.

  • Actions: Dorsiflexion (lifting the foot upwards), toe extension, and inversion.

• Superficial Fibular (Peroneal) Nerve: Innervates the muscles in the lateral compartment of the leg.

  • Muscles: Peroneus Longus and Peroneus Brevis.

  • Action: Eversion (turning the sole of the foot outward).

B. Sensory Innervation

The common fibular nerve and its branches provide sensation to:

• The Superficial Fibular Nerve supplies sensation to the skin on the lower anterior/lateral leg and the dorsum (top) of the foot.

• The Deep Fibular Nerve supplies a small web of skin between the first and second toes.

C. Clinical Significance: A Vulnerable Nerve

The Common Peroneal Nerve is highly susceptible to injury due to its superficial and vulnerable course as it wraps around the neck of the fibula.

• Causes of Injury: Knee dislocation, fibula fracture, tight casts, prolonged squatting, crossing legs, or even direct pressure from a hospital bed.

• Resulting Deficits (Foot Drop):

  • Motor: The most classic sign is "Foot Drop." Due to paralysis of the dorsiflexors, the patient cannot lift the foot at the ankle. This results in a "steppage gait," where the person must lift the knee unusually high to prevent the toes from catching on the ground while walking.

  • Sensory: Loss of sensation on the anterolateral leg and the dorsum of the foot.

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Summary

Feature	Description
Etymology	"Peroneal" (Gr. perone, pin, referring to the fibula) or the modern "Fibular" (of the fibula). "Common" refers to its subsequent division.
Primary Function	Motor nerve to the anterior (dorsiflexors) and lateral (evertors) compartments of the leg.
Key Role	Enables dorsiflexion (preventing foot drop) and eversion of the foot.
Nerve Roots	L4, L5, S1, S2 (as part of the sciatic nerve).
Clinical Note	Highly vulnerable to injury at the fibular neck, leading to Foot Drop and a characteristic steppage gait.

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Posterior Femoral Cutaneous Nerve.

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Posterior Femoral Cutaneous Nerve1. Etymology (Word Origin)

The name is a direct and descriptive anatomical label:

• Posterior: From Latin, meaning "behind" or "back."

• Femoral: From Latin femur/femoris, meaning "thigh."

• Cutaneous: From Latin cutis, meaning "skin."

Therefore, Posterior Femoral Cutaneous Nerve literally translates to "the skin nerve of the back of the thigh." This name perfectly describes its primary role as a sensory nerve.

2. Function

As its name implies, the Posterior Femoral Cutaneous Nerve is a pure sensory nerve. It does not innervate any muscles.

A. Primary Function: Sensory Innervation

Its sole function is to provide sensation to the skin of a large portion of the posterior lower limb:

1. Posterior Thigh: It supplies the skin over the entire back of the thigh, from the gluteal fold (bottom of the buttock) down to the back of the knee (popliteal fossa).

2. Inferior Gluteal Region: It gives off inferior clunial nerves which supply the skin over the lower part of the buttock.

3. Perineum: It has a perineal branch that supplies a variable area of skin in the upper and medial thigh, and sometimes part of the external genitalia (scrotum in males, labia majora in females). This is why it is sometimes called the "small sciatic nerve."

B. Anatomical Course

• It exits the pelvis through the greater sciatic foramen, inferior to the Piriformis muscle.

• It then runs down the back of the thigh deep to the deep fascia, but superficial to the sciatic nerve, which it accompanies for much of its course.

C. Clinical Significance

• Meralgia Paresthetica Comparison: While meralgia paresthetica involves the lateral femoral cutaneous nerve, compression or irritation of the posterior femoral cutaneous nerve can cause a similar condition with numbness, tingling (paresthesia), or pain in the back of the thigh and lower buttock.

• Differentiating Sciatica: Pain in the posterior thigh can be caused by sciatic nerve pathology (sciatica) or by irritation of the posterior femoral cutaneous nerve. A key differentiator is that sciatica typically involves motor weakness and pain radiating below the knee, while posterior femoral cutaneous nerve issues are purely sensory and generally confined to the thigh and buttock.

• Surgical Landmark: Its location is important for surgeons performing posterior approaches to the hip and thigh to avoid inadvertent injury.

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Summary

Feature	Description
Etymology	"Posterior" (back) + "Femoral" (thigh) + "Cutaneous" (skin) = "The skin nerve of the back of the thigh."
Primary Function	Exclusively sensory. Provides feeling to the skin of the posterior thigh, lower buttock, and parts of the perineum.
Key Role	Carries sensory information (touch, temperature, pain) from a large area of the posterior lower limb.
Nerve Roots	S1, S2, S3 (It arises from the sacral plexus).
Clinical Note	Irritation can cause sensory symptoms in the back of the thigh, which must be differentiated from true sciatica.

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Superior Gemellus muscle.

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Superior Gemellus Muscle1. Etymology (Word Origin)

The name "Gemellus" is derived directly from Latin:

• Gemellus: The diminutive form of geminus, meaning "twin."

• Superior: From Latin, meaning "upper" or "above."

Therefore, Superior Gemellus literally translates to "the upper twin." This name reflects its anatomical relationship with the Inferior Gemellus ("the lower twin"), as these two small muscles are located above and below the tendon of the Obturator Internus, forming a functional "trio."

2. Function

The Superior Gemellus is one of the six short, deep muscles in the gluteal region known as the lateral rotators of the hip. It is a small, narrow muscle.

A. Primary Action:

• Lateral (External) Rotation of the Thigh: This is the primary and most significant action of the superior gemellus. It works with the other deep rotators to powerfully rotate the extended thigh outward, turning the foot and knee away from the midline of the body.

B. Secondary Action:

• Abduction of the Flexed Thigh: When the hip is flexed (bent), the line of pull of these muscles changes, and they can contribute to abducting the thigh (moving it away from the midline).

C. Functional Anatomy and Relationship:

The Superior Gemellus does not work in isolation. It is functionally and anatomically fused with the tendon of the Obturator Internus muscle and the Inferior Gemellus muscle.

• The tendon of the Obturator Internus passes between the two gemelli muscles.

• All three structures (Superior Gemellus, Obturator Internus tendon, Inferior Gemellus) converge to form a common tendon that inserts onto the greater trochanter of the femur.

• Because of this close relationship, the gemelli muscles are often considered functional "accessories" to the Obturator Internus, reinforcing its action.

D. Clinical Significance

• While not a common site of isolated pathology, the gemelli muscles can be involved in deep gluteal pain syndrome.

• Their main clinical importance is anatomical. They help define the boundaries of the greater sciatic foramen, through which critical structures like the sciatic nerve and pudendal nerve pass.

• Understanding their location is important for surgeons operating in the deep gluteal region to avoid damaging neurovascular structures.

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Summary

Feature	Description
Etymology	"Superior" (L. upper) + "Gemellus" (L. little twin) = "The upper little twin."
Primary Function	Lateral (External) Rotation of the thigh at the hip joint.
Key Role	Acts as a functional synergist to the Obturator Internus and Inferior Gemellus, together forming a common conjoined tendon. Helps stabilize the hip joint.
Innervation	Nerve to Obturator Internus (L5, S1)
Clinical Note	Part of the deep gluteal muscle group; its main significance is as an anatomical landmark for the sciatic foramen.

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Inferior Gemellus muscle.

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Inferior Gemellus Muscle1. Etymology (Word Origin)

The name "Gemellus" is derived directly from Latin:

• Gemellus: The diminutive form of geminus, meaning "twin."

• Inferior: From Latin, meaning "lower" or "below."

Therefore, Inferior Gemellus literally translates to "the lower twin." This name perfectly describes its anatomical position relative to the Superior Gemellus ("the upper twin"), as these two small muscles bracket the tendon of the Obturator Internus.

2. Function

The Inferior Gemellus is a small muscle that is part of the "deep six" lateral rotators of the hip. Its function is nearly identical to that of the Superior Gemellus.

A. Primary Action:

• Lateral (External) Rotation of the Thigh: This is its primary action. It works with the other deep rotators (piriformis, obturator internus, etc.) to powerfully rotate the extended thigh outward.

B. Secondary Action:

• Abduction of the Flexed Thigh: When the hip is flexed to 90 degrees, the line of pull of these muscles changes, and they can assist in abducting the thigh.

C. Functional Anatomy and Relationship:

The Inferior Gemellus is functionally and anatomically fused with the tendons of the Obturator Internus and Superior Gemellus.

• The tendon of the Obturator Internus passes between the two gemelli muscles.

• All three structures converge to insert as a common tendon onto the medial surface of the greater trochanter of the femur.

• Because of this arrangement, the gemelli muscles are considered functional accessories to the Obturator Internus, augmenting its action.

D. Clinical Significance

• The clinical significance of the inferior gemellus is primarily anatomical.

• It helps form the boundaries of the greater sciatic foramen.

• Understanding its location is important for differentiating the pathways of the nerves in the gluteal region, particularly the Nerve to Quadratus Femoris, which innervates it and runs deep to it.

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Summary

Feature	Description
Etymology	"Inferior" (L. lower) + "Gemellus" (L. little twin) = "The lower little twin."
Primary Function	Lateral (External) Rotation of the thigh at the hip joint.
Key Role	Acts as a functional synergist to the Obturator Internus and Superior Gemellus, forming a conjoined tendon for hip stabilization and rotation.
Innervation	Nerve to Quadratus Femoris (L4, L5, S1)
Clinical Note	Its main importance is as an anatomical landmark in the deep gluteal region.

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Tendon of the Obturator Internus muscle.

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Tendon of Obturator Internus Muscle1. Etymology (Word Origin)

The name describes the muscle to which the tendon belongs:

• Obturator: From Latin obturare, meaning "to occlude" or "to stop up." This refers to the obturator foramen, the large opening in the pelvis that is almost completely closed by the obturator membrane.

• Internus: From Latin, meaning "internal." This indicates the muscle originates on the internal (pelvic) surface of the obturator membrane.

• Tendon: A tough band of fibrous connective tissue that connects muscle to bone.

Therefore, Tendon of Obturator Internus literally means "the tendon of the internal muscle that covers the obturator foramen."

2. Function

The tendon of the obturator internus is the functional continuation of the muscle, and its unique pathway is key to its action.

A. Primary Action:

• Lateral (External) Rotation of the Thigh: This is the primary action. When the obturator internus contracts, its tendon pulls on the femur, causing the thigh to rotate outward.

B. Secondary Action:

• Abduction of the Flexed Thigh: When the hip is flexed to 90 degrees, the line of pull of the tendon changes. In this position, its contraction contributes to moving the thigh away from the midline (abduction).

• Stabilization: As part of the deep rotator group, it helps stabilize the head of the femur in the acetabulum (hip socket) during movement.

C. Unique Anatomical Course & Functional Relationship

The pathway of this tendon is its most defining characteristic and is fundamental to its function:

1. Origin: The Obturator Internus muscle originates on the internal surface of the obturator membrane and the surrounding bone.

2. Exit from Pelvis: The muscle fibers converge into a tendon that exits the pelvic cavity through the lesser sciatic foramen.

3. The "Gemellus Complex": Immediately after exiting, the tendon makes a sharp 90-degree turn around the bony groove of the ischium. It is at this point that it is joined by and functionally fused with the two gemellus muscles:

   • The Superior Gemellus attaches to its superior surface.

   • The Inferior Gemellus attaches to its inferior surface.

4. Insertion: This conjoined tendon (Obturator Internus + Superior Gemellus + Inferior Gemellus) inserts onto the medial surface of the greater trochanter of the femur.

This arrangement means the three muscles (Obturator Internus, Superior Gemellus, Inferior Gemellus) function as a single unit, often referred to as the "triceps coxae."

D. Clinical Significance

• Landmark: The tendon and its associated gemelli muscles are important landmarks in the deep gluteal region, helping to define the greater and lesser sciatic foramina.

• Pathology: While isolated injury is rare, dysfunction or tendinopathy of the obturator internus can contribute to deep gluteal pain. Its close relationship to the sciatic and pudendal nerves means inflammation or spasm could potentially contribute to nerve irritation.

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Summary

Feature	Description
Etymology	"Obturator" (L. to occlude) + "Internus" (L. internal) + "Tendon" = "The tendon of the internal muscle that plugs the opening."
Primary Function	Lateral (External) Rotation of the thigh.
Key Role	Forms the central component of the "triceps coxae" with the gemelli muscles. Its unique path through the lesser sciatic foramen allows it to effectively pull the femur into rotation.
Innervation	Nerve to Obturator Internus (L5, S1)
Clinical Note	An important anatomical landmark. Part of the deep hip rotator group whose dysfunction can contribute to gluteal pain

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Quadratus Femoris muscle.

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Quadratus Femoris Muscle1. Etymology (Word Origin)

The name is a direct description of the muscle's shape and location:

• Quadratus: From Latin quadrus, meaning "square" or "four-sided."

• Femoris: From Latin femur/femoris, meaning "thigh."

Therefore, Quadratus Femoris literally translates to "the square-shaped muscle of the thigh." This accurately describes its appearance as a flat, rectangular muscle.

2. Function

The Quadratus Femoris is the most inferior of the deep gluteal muscles (the lateral rotators) and is a strong and important stabilizer of the hip.

A. Primary Action:

• Lateral (External) Rotation of the Thigh: This is its primary and most powerful action. It is one of the most effective lateral rotators of the hip joint.

B. Secondary Action:

• Adduction of the Thigh: It assists in pulling the thigh towards the midline of the body.

C. Functional Anatomy and Clinical Significance

1. Stabilizer: Due to its horizontal orientation and direct path from the ischial tuberosity (the bone you sit on) to the femur, it is a key stabilizer of the hip joint, particularly helping to prevent lateral displacement of the femoral head.

2. Important Surgical Landmark: The Quadratus Femoris is a critical landmark in the deep gluteal region. It is closely related to several vital structures:

   • Anteriorly: The tendon of the Obturator Externus muscle passes directly deep to it.

   • Medially: The Sciatic Nerve typically runs directly anterior to it. This proximity makes the quadratus femoris a key reference point for identifying and protecting the sciatic nerve during posterior approaches to the hip.

   • The Medial Femoral Circumflex Artery, a crucial blood supply to the femoral head, also passes either through the muscle or immediately superior to it.

3. Nerve Innervation: It is supplied by a specific Nerve to Quadratus Femoris (L4, L5, S1), which also innervates the Inferior Gemellus muscle.

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Summary

Feature	Description
Etymology	"Quadratus" (L. square) + "Femoris" (L. of the thigh) = "The square-shaped muscle of the thigh."
Primary Function	Powerful Lateral (External) Rotation of the thigh. Also assists in Adduction.
Key Role	A key stabilizer of the hip joint. Serves as a critical surgical landmark for identifying the Sciatic Nerve and the Medial Femoral Circumflex Artery.
Innervation	Nerve to Quadratus Femoris (L4, L5, S1)
Clinical Note	Its location is vital in hip surgery to avoid damaging the sciatic nerve. Pathology here can be a source of deep gluteal pain.

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Tendon of the Obturator Externus muscle.

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Tendon of Obturator Externus Muscle1. Etymology (Word Origin)

The name describes the muscle to which the tendon belongs, distinguishing it from its internal counterpart:

• Obturator: From Latin obturare, meaning "to occlude" or "to stop up." This refers to the obturator foramen, the large opening in the pelvis.

• Externus: From Latin, meaning "external." This indicates the muscle originates on the external (outer) surface of the obturator membrane and the surrounding pubic and ischial bones.

• Tendon: A tough band of fibrous connective tissue that connects muscle to bone.

Therefore, Tendon of Obturator Externus literally means "the tendon of the external muscle that covers the obturator foramen."

2. Function

The obturator externus is a flat, triangular muscle, and its tendon has a unique and important path that defines its function.

A. Primary Action:

• Lateral (External) Rotation of the Thigh: This is its primary action. When the muscle contracts, its tendon pulls on the femur, rotating the thigh outward.

B. Secondary Action:

• Adduction of the Thigh: It assists in pulling the thigh toward the midline of the body.

• Stabilization: It helps to stabilize the head of the femur in the hip socket (acetabulum), particularly by pressing the femoral head medially.

C. Unique Anatomical Course & Functional Relationship

The pathway of this tendon is its most remarkable feature and is key to its function as a lateral rotator:

1. Origin: The Obturator Externus muscle originates on the external (anterior) surface of the obturator membrane and the surrounding bone.

2. Course: The muscle fibers converge into a tendon that passes postero-inferiorly (backwards and downwards).

3. The Trochanteric Fossa: The tendon then passes deep to the neck of the femur and, most importantly, deep to the Quadratus Femoris muscle.

4. Insertion: It inserts into the trochanteric fossa, a depression on the medial surface of the greater trochanter of the femur.

This path—wrapping around the back of the femoral neck—creates a pulley-like effect, making it an effective lateral rotator despite its anterior origin.

D. Clinical Significance

• Surgical Landmark and Protector: The obturator externus tendon and the muscle itself form part of the posterior-inferior capsule of the hip joint. During posterior surgical approaches to the hip, the tendon is a key landmark. Surgeons often preserve it and the underlying capsule to protect the critical Medial Femoral Circumflex Artery (MFCA), the main blood supply to the femoral head. Damage to this artery can lead to avascular necrosis (bone death) of the femoral head.

• "The Key to the Hip Joint": In some surgical contexts, the obturator externus tendon is used as a "key" to safely identify and access the hip joint capsule without damaging vital vessels.

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Summary

Feature	Description
Etymology	"Obturator" (L. to occlude) + "Externus" (L. external) + "Tendon" = "The tendon of the external muscle that plugs the opening."
Primary Function	Lateral (External) Rotation of the thigh. Also assists in Adduction.
Key Role	Its unique path deep to the quadratus femoris and around the femoral neck makes it an effective rotator. It acts as a vital surgical landmark protecting the blood supply to the femoral head.
Innervation	Obturator Nerve (Posterior Division) (L3, L4)
Clinical Note	Crucial in hip surgery; its preservation helps protect the Medial Femoral Circumflex Artery, preventing avascular necrosis of the hip.

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Pudendal Nerve.

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Pudendal Nerve1. Etymology (Word Origin)

The name "Pudendal" is derived from Latin, with a meaning rooted in concepts of modesty and shame:

• Pudendal: From the Latin word pudendum, which means "external genitals." The word pudendum itself comes from the Latin verb pudēre, meaning "to be ashamed."

This etymology reflects the historical association of the external genitalia with shame and modesty, which is why they were to be "covered." Therefore, the Pudendal Nerve literally translates to "the nerve of the external genitalia," which is a perfectly accurate description of its function.

2. Function

The Pudendal Nerve is the principal somatic nerve of the perineum and the external genitalia. This means it provides both voluntary motor control and sensation to this region.

A. Motor Innervation:

It supplies the voluntary (skeletal) muscles of the pelvic floor and perineum, which are crucial for continence and sexual function:

• External Urethral Sphincter: Provides voluntary control over urination.

• External Anal Sphincter: Provides voluntary control over defecation.

• All other skeletal muscles of the perineum, including the bulbospongiosus, ischiocavernosus, and the deep and superficial perineal muscles.

B. Sensory Innervation:

It provides sensation to the skin and mucosa of:

• The penis and scrotum in males.

• The clitoris, labia majora, and labia minora in females.

• The skin around the anus (the perianal skin).

C. Unique Anatomical Course: The "Alcock's Canal" Journey

The path of the pudendal nerve is clinically significant and is often summarized by the mnemonic "S2, S3, S4 keeps the shit off the floor" (referring to its sacral nerve roots and its motor function for the pelvic floor). Its course is a key to understanding "Pudendal Neuralgia":

1. Exit: It exits the pelvis through the greater sciatic foramen (inferior to the Piriformis muscle).

2. Hook: It hooks around the ischial spine or the sacrospinous ligament.

3. Re-enter: It immediately re-enters the pelvis through the lesser sciatic foramen.

4. Travel: It travels through a fascial canal called Alcock's canal (or the pudendal canal) on the lateral wall of the ischioanal fossa.
   This long, winding course makes it susceptible to entrapment or injury.

D. Clinical Significance: Pudendal Neuralgia

• What it is: A chronic, debilitating pain condition caused by compression, irritation, or injury to the pudendal nerve.

• Symptoms: Severe pain in the regions supplied by the nerve (genitals, perineum, anus), often described as burning, stabbing, or a feeling of a foreign object in the rectum or vagina. The pain is typically worsened by sitting and relieved by standing or lying down.

• Causes: Can include prolonged cycling, childbirth, pelvic surgery, trauma, or repetitive strain.

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Summary

Feature	Description
Etymology	From L. pudendum (external genitals, from "to be ashamed") = "The nerve of the external genitalia."
Primary Function	Motor control to the voluntary muscles of the pelvic floor (sphincters) and sensation from the external genitalia and perianal skin.
Key Role	Essential for urinary and fecal continence, sexual function, and sensation.
Nerve Roots	S2, S3, S4 (the classic mnemonic helps remember this).
Clinical Note	Entrapment or injury leads to Pudendal Neuralgia, a severe chronic pain condition. Its course around the ischial spine is a common site of compression.

Gluteal region

 Gluteus maximus muscle

 Iliotibial band of the fascia lata

 Gluteal tuberosity of femur

 Gluteus medius muscle

 Gluteus minimus muscle

 Piriformis muscle

 Superior gluteal nerve

 Superior gluteal vessels

 Inferior gluteal nerve

 Inferior gluteal vessels

 Sciatic nerve

 Tibial nerve

 Common peroneal (fibular) nerve

 Posterior femoral cutaneous nerve

 Superior gemellus muscle

 Inferior gemellus muscle

 Tendon of obturator internus muscle

 Quadratus femoris muscle

 Tendon of obturator externus muscle

 Pudendal nerve

 Internal pudendal vessel

Here is a detailed breakdown of the etymology and function of the Internal Pudendal Vessels.

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Internal Pudendal Vessels1. Etymology (Word Origin)

The name is directly related to that of the Pudendal Nerve and describes the vessels' anatomical path:

• Internal: From Latin, meaning "inner" or "within." This indicates that this vessel is the main channel that runs inside the pelvic cavity for part of its course, as opposed to any potential superficial "external" pudendal vessels.

• Pudendal: From the Latin word pudendum (from pudēre, "to be ashamed"), meaning "external genitals."

• Vessels: A collective term for the artery and vein.

Therefore, Internal Pudendal Vessels literally translates to "the inner blood vessels of the external genitalia."

2. Function

The Internal Pudendal Artery and Vein are the primary blood supply and drainage for the structures of the perineum and external genitalia.

A. Internal Pudendal Artery (Function: Supply)

This artery is the main source of oxygenated blood for the perineum. It is a branch of the internal iliac artery.

• Structures Supplied:

  • Muscles: All muscles of the perineum (e.g., external anal sphincter, bulbospongiosus, ischiocavernosus).

  • Erectile Tissues: The penis and clitoris (via its terminal branches: the artery of the bulb, deep artery of the penis/clitoris, and dorsal artery of the penis/clitoris).

  • Skin and Mucosa: The skin of the anal region, scrotum, and labia.

B. Internal Pudendal Vein (Function: Drainage)

This vein follows the course of the artery in reverse.

• Function: It drains deoxygenated blood from the same perineal structures supplied by the artery.

• Termination: It empties into the internal iliac vein.

C. Unique Anatomical Course

The vessels share the same intricate and clinically important path as the pudendal nerve, often summarized as a journey out of, around, and back into the pelvis:

1. Exit the Pelvis: They exit the pelvis through the greater sciatic foramen, inferior to the Piriformis muscle.

2. Hook Around: They hook around the ischial spine or the sacrospinous ligament.

3. Re-enter the Pelvis: They immediately re-enter the perineum through the lesser sciatic foramen.

4. Travel in Alcock's Canal: They travel through the pudendal canal (Alcock's canal) on the lateral wall of the ischioanal fossa, alongside the pudendal nerve.

This course allows the vessels to efficiently serve the perineal structures without taking a more direct but obstructed path through the pelvis.

D. Clinical Significance

• Pudendal Neuralgia: The vessels travel in a tight neurovascular bundle with the pudendal nerve. Vascular entrapment or dilation can contribute to nerve compression, leading to chronic pain (Pudendal Neuralgia).

• Surgical Landmark: Their path is a critical landmark in perineal and pelvic surgery (e.g., for repair of pelvic organ prolapse or incontinence). Damage can lead to significant bleeding.

• Erectile Function: The internal pudendal artery is the primary arterial supply for erection. Its branches are responsible for the increased blood flow that facilitates erection in both males and females.

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Summary

Feature	Description
Etymology	"Internal" (L. inner) + "Pudendal" (L. of the external genitals) = "The inner vessels of the external genitalia."
Primary Function	Artery: Main blood supply to the perineum, external genitalia, and erectile tissues. Vein: Drains blood from the same region.
Key Role	Essential for the function of the pelvic floor, continence mechanisms, and sexual response (erection).
Origin/End	Artery: Branch of the Internal Iliac Artery. Vein: Drains into the Internal Iliac Vein.
Clinical Note	Their shared course with the pudendal nerve makes them relevant in Pudendal Neuralgia. They are vital for erectile function and are at risk during pelvic surgery.

Posterior thigh and popliteal fossa

 Hamstring muscles

 Biceps femoris

 Long head

 Short head

 Semitendinosus

 Semimembranosus

 Popliteal fossa

 Popliteal artery

 Popliteal vein

 Tibial nerve

 Common peroneal (fibular) nerve

 Small saphenous vein

 Popliteus muscle

This is an excellent and structured list of the key anatomical components of the posterior thigh and popliteal fossa. Let's expand on this outline with detailed descriptions and functions.

Posterior Thigh & Popliteal Fossa: A Detailed Overview

The posterior compartment of the thigh is dominated by the hamstring muscles, which are crucial for hip extension and knee flexion. The popliteal fossa is the shallow diamond-shaped depression behind the knee where important neurovascular structures transition from the thigh to the leg.

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1. Hamstring Muscles

The hamstrings are a group of three (or four, considering the two heads of biceps femoris) muscles in the posterior thigh. A key defining feature of "true" hamstrings is that they cross both the hip and knee joints.

• General Origin: Ischial tuberosity (except the short head of biceps femoris).

• General Innervation: Tibial division of the Sciatic nerve (except the short head of biceps femoris).

• General Action:

  • Extension of the thigh at the hip (e.g., pulling your thigh back when walking).

  • Flexion of the leg at the knee (e.g., bending your knee).

Biceps Femoris

The most lateral hamstring muscle, it has two heads.

• Long Head:

  • Origin: Ischial tuberosity (common origin with semitendinosus).

  • Insertion: Head of the fibula (lateral side of the leg).

  • Action: Hip extension, knee flexion, and lateral rotation of the leg when the knee is flexed.

  • Innervation: Tibial nerve.

• Short Head:

  • Origin: Linea aspera of the femur.

  • Insertion: Head of the fibula (with the long head).

  • Action: Knee flexion and lateral rotation only (it does not cross the hip joint).

  • Innervation: Common peroneal (fibular) nerve. This is a key distinguishing feature.

Semitendinosus

Lies medial to the biceps femoris. It is recognizable by its long, cord-like tendon that makes up about half the muscle's length.

• Origin: Ischial tuberosity (shared with long head of biceps femoris).

• Insertion: Medial surface of the upper part of the tibia (part of the "pes anserinus").

• Action: Hip extension, knee flexion, and medial rotation of the leg when the knee is flexed.

• Innervation: Tibial nerve.

Semimembranosus

The deepest and most medial hamstring muscle. It has a broad, flat membranous proximal tendon.

• Origin: Ischial tuberosity (superior and lateral to the common origin).

• Insertion: Medial condyle of the tibia.

• Action: Hip extension, knee flexion, and medial rotation of the leg.

• Innervation: Tibial nerve.

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2. Popliteal Fossa

This is a critical anatomical region for vascular and nervous supply to the leg and foot.

Boundaries:

• Superolateral: Biceps femoris muscle.

• Superomedial: Semitendinosus and Semimembranosus muscles.

• Inferolateral: Lateral head of the Gastrocnemius muscle.

• Inferomedial: Medial head of the Gastrocnemius muscle.

• Floor: Popliteal surface of the femur and the Popliteus muscle, covered by the popliteal fascia.

• Roof: Popliteal fascia and skin.

Contents of the Popliteal Fossa (from deep to superficial):

A common mnemonic is "Serve And Volley Next Ball" or "Some Anatomists Like Freaking Out Poor Medical Students" which represents, from deep to superficial:

1. Popliteal Artery:

   • The direct continuation of the femoral artery after it passes through the adductor hiatus.

   • It is the deepest structure in the fossa.

   • It supplies the knee joint via genicular branches.

   • It ends by dividing into the Anterior Tibial Artery and Posterior Tibial Artery at the lower border of the popliteus muscle.

2. Popliteal Vein:

   • Lies superficial to the popliteal artery.

   • It is formed by the union of the anterior and posterior tibial veins.

   • It drains blood from the leg and becomes the femoral vein as it passes through the adductor hiatus.

3. Tibial Nerve:

   • The larger terminal branch of the sciatic nerve.

   • It lies most superficial (posterior) among the major neurovascular structures.

   • It provides motor innervation to the muscles of the posterior compartment of the leg (e.g., gastrocnemius, soleus) and all the intrinsic muscles of the foot.

   • It gives off branches in the popliteal fossa to the gastrocnemius, popliteus, plantaris, and soleus muscles.

4. Common Peroneal (Fibular) Nerve:

   • The smaller terminal branch of the sciatic nerve.

   • It runs along the superolateral border of the popliteal fossa, medial to the biceps femoris tendon.

   • It is relatively superficial and vulnerable to injury at the back of the knee and as it winds around the neck of the fibula.

   • It provides innervation to the short head of biceps femoris in the fossa and then divides into the superficial and deep fibular nerves to supply the lateral and anterior compartments of the leg.

Other Structures:

• Small Saphenous Vein:

  • A superficial vein that drains the lateral side of the foot and leg.

  • It ascends the posterior leg and pierces the deep popliteal fascia to empty into the Popliteal Vein.

• Popliteus Muscle:

  • A small, flat muscle that forms part of the floor of the popliteal fossa.

  • Action: It "unlocks" the fully extended knee by laterally rotating the femur on the tibia to initiate knee flexion. It also provides stability to the knee.

Clinical Correlations

• Hamstring Strain ("Pulled Hamstring"): A common injury, often at the proximal musculotendinous junction near the ischial tuberosity, caused by excessive stretching or overload.

• Popliteal Aneurysm: A abnormal dilation of the popliteal artery; it is the most common peripheral aneurysm and a site for potential thrombosis or embolism.

• Common Peroneal Nerve Injury: Due to its superficial location, it can be damaged by knee dislocation, fractures of the fibular neck, or casting. Injury leads to foot drop (inability to dorsiflex the foot) and loss of sensation on the anterolateral leg and dorsum of the foot.

• Baker's Cyst (Popliteal Cyst): A fluid-filled swelling in the popliteal fossa, often caused by bursitis associated with knee joint pathology like osteoarthritis or rheumatoid arthritis.

Posterior thigh and popliteal fossa

 Hamstring muscles

 Biceps femoris

 Long head

 Short head

 Semitendinosus

 Semimembranosus

 Popliteal fossa

 Popliteal artery

 Popliteal vein

 Tibial nerve

 Common peroneal (fibular) nerve

 Small saphenous vein

 Popliteus muscle

The hamstring muscles have a name rooted in their practical, historical function, and their roles in the body are crucial for locomotion.

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Etymology of "Hamstring"

The term "hamstring" comes from Old English and is a combination of two words:

1. Ham (or Hamm): This did not refer to the meat, but to the hollow or bend of the knee, essentially the back of the thigh or the popliteal fossa itself.

2. String: This refers to the prominent, cord-like tendons of these muscles that are easily felt on either side of the popliteal fossa (especially the semitendinosus and biceps femoris tendons).

So, literally, "hamstring" means "the tendons in the hollow of the knee."

Historically, the term was used by butchers. The "ham" of an animal (like a pig) is the thigh and buttock region, and the "hamstrings" are the tendons used to hang the ham for curing. In a practical, gruesome context, "to hamstring" an animal or person meant to cut these tendons behind the knee to cripple them and prevent them from running or walking properly.

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Function of the Hamstring Muscles

The hamstrings are bi-articular muscles, meaning they cross and act upon two joints: the hip and the knee. This dual-joint function makes them essential for powerful, coordinated movements like running and jumping.

Here is a breakdown of their functions by joint and muscle:

Primary Functions

1. Knee Flexion:

   • This is their most well-known action: bending the knee, bringing the heel towards the buttock.

   • All four components (long and short heads of biceps femoris, semitendinosus, semimembranosus) contribute powerfully to this action.

2. Hip Extension:

   • This is the action of moving the thigh backward, as in the propulsion phase of walking, running, or rising from a bent-over position.

   • This action is performed only by the three muscles that cross the hip joint: the long head of biceps femoris, semitendinosus, and semimembranosus. The short head of biceps femoris does not cross the hip and therefore cannot extend it.

Secondary Functions (Rotation)

When the knee is flexed (bent), the hamstrings can also rotate the leg at the knee:

• Medial (Internal) Rotation:

  • Performed by the Semitendinosus and Semimembranosus.

  • This turns the foot and tibia inward.

• Lateral (External) Rotation:

  • Performed by the Biceps Femoris (both heads).

  • This turns the foot and tibia outward.

Functional Summary in Movement

• Walking/Running: During the "stance phase," the hamstrings are critical for hip extension to propel the body forward. As the leg swings through, they help decelerate the leg to prepare for foot strike.

• Stability: They are crucial stabilizers of both the hip and the knee joints.

• Posture: They work antagonistically with the quadriceps and hip flexors to maintain pelvic alignment. Tight hamstrings are a common cause of posterior pelvic tilt.

Clinical & Functional Note: The "Hamstring Strain"

The dual-joint nature of the hamstrings is also their vulnerability. During activities like sprinting, the hamstrings are maximally stretched (hip flexed and knee extending) while also trying to contract forcefully (to extend the hip). This high-stress situation makes them prone to strains or "pulls," most commonly at the proximal musculotendinous junction near the ischial tuberosity.

Posterior thigh and popliteal fossa

 Hamstring muscles

 Biceps femoris

 Long head

 Short head

 Semitendinosus

 Semimembranosus

 Popliteal fossa

 Popliteal artery

 Popliteal vein

 Tibial nerve

 Common peroneal (fibular) nerve

 Small saphenous vein

 Popliteus muscle

Here is a detailed overview of the Biceps Femoris muscle, breaking down its structure, function, innervation, and clinical significance.

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Biceps Femoris: The Two-Headed Muscle of the Posterior Thigh

The Biceps Femoris is the most lateral and, as the name implies, the two-headed muscle of the hamstring group. It is a key muscle for movement and stability at both the hip and knee joints.

Anatomy & Structure

The two heads have distinct origins but share a common insertion point.

• Long Head:

  • Origin: Ischial tuberosity (the bony prominence you sit on), via the common hamstring tendon with the semitendinosus.

  • Characteristics: This head is a "true" hamstring as it crosses both the hip and knee joints.

• Short Head:

  • Origin: Linea aspera and the lateral supracondylar line on the posterior aspect of the femur (thigh bone).

  • Characteristics: This head is unique; it only crosses the knee joint, not the hip.

• Common Insertion:

  • Head of the fibula and the lateral condyle of the tibia.

  • The muscle forms a prominent, palpable tendon on the lateral side of the popliteal fossa (the back of the knee) before inserting.

Innervation (Nerve Supply)

This is a critical distinguishing feature between the two heads:

• Long Head: Innervated by the tibial nerve (a division of the sciatic nerve).

• Short Head: Innervated by the common peroneal (fibular) nerve (the other division of the sciatic nerve).

Why this matters: This dual innervation is a key anatomical clue. If a patient has weakness in knee flexion but hip extension is intact, the lesion might be in the common peroneal nerve, affecting only the short head.

Functions

Due to its two heads crossing different joints, the Biceps Femoris has composite actions:

1. Knee Flexion: Both the long and short heads powerfully bend the knee.

2. Lateral Rotation of the Leg: When the knee is flexed (bent), the biceps femoris acts to rotate the tibia outward, turning the foot away from the midline.

3. Hip Extension: This action is performed only by the Long Head. It helps pull the thigh backward, such as when rising from a bent-over position or during the push-off phase of walking and running.

4. Stability: It provides crucial dynamic stability to both the knee and hip joints.

Clinical Notes

• Hamstring Strain: The biceps femoris, particularly the long head, is one of the most commonly injured hamstring muscles. Strains often occur during high-speed activities like sprinting, when the muscle is forcibly stretched (hip flexing and knee extending) while simultaneously contracting.

• Injury Location: The most common site of injury is the proximal musculotendinous junction of the long head, near the ischial tuberosity. This is often felt as a sudden, sharp pain in the buttock/upper thigh region.

• Common Peroneal Nerve Vulnerability: The common peroneal nerve, which innervates the short head, runs very close to the biceps femoris tendon behind the knee and around the fibular head. Trauma to this area can injure the nerve, leading to foot drop and loss of sensation in the lower leg.

Summary Table

Feature	Long Head	Short Head
Origin	Ischial Tuberosity	Linea Aspera of Femur
Innervation	Tibial Nerve	Common Peroneal Nerve
Crosses Hip?	Yes	No
Actions	- Hip Extension - Knee Flexion - Lateral Leg Rotation	- Knee Flexion - Lateral Leg Rotation

Posterior thigh and popliteal fossa

 Hamstring muscles

 Biceps femoris

 Long head

 Short head

 Semitendinosus

 Semimembranosus

 Popliteal fossa

 Popliteal artery

 Popliteal vein

 Tibial nerve

 Common peroneal (fibular) nerve

 Small saphenous vein

 Popliteus muscle

Let's break down the "Long Head" of the Biceps Femoris, focusing on the specific meaning of its name and its distinct functions.

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Etymology of "Long Head"

The name is a straightforward anatomical descriptor based on the muscle's physical structure:

• "Long": This refers to the length of its muscle fibers and its tendon of origin. The long head has a more superior origin (at the ischial tuberosity) and a longer course before merging with the short head to form the common tendon. It is literally the "longer" of the two heads.

• "Head": In myology (the study of muscles), a "head" is a distinct origin point of a muscle that arises from multiple locations. These separate heads then converge to form a single muscle belly and tendon.

Therefore, "Long Head" simply means the section of the biceps femoris muscle that originates from a point farther away and has a longer structural component than its partner, the "Short Head."

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Function of the Long Head of Biceps Femoris

As a key part of the hamstring group, the long head is a bi-articular muscle, meaning it crosses and acts upon two joints: the hip and the knee. This is its primary functional distinction from the short head.

Primary Functions:

1. Hip Extension:

   • This is the most powerful action of the long head at the hip. It works to move the thigh backward relative to the pelvis.

   • Example Movements: Pushing off during walking or running, rising from a bent-over position (e.g., a deadlift), climbing stairs.

2. Knee Flexion:

   • The long head works with the other hamstrings to bend the knee, bringing the heel toward the buttock.

   • Example Movements: The leg swing during walking, preparing to kick a ball, squatting down.

3. Lateral (External) Rotation of the Leg:

   • This action occurs only when the knee is already flexed. The long head, pulling from its lateral insertion on the fibular head, rotates the tibia outward, turning the foot away from the midline of the body.

   • Example Movement: The pivoting of the leg when planting the foot to change direction.

Functional Summary & Clinical Insight

• Dual-Joint Role: The long head is crucial for coordinated lower body movement. During sprinting, it is particularly active, working to extend the hip for propulsion while also helping to control the degree of knee extension on the forward swing of the leg.

• Why it's Prone to Injury: This dual role is also its weakness. During high-speed activities, the long head can be stretched to its limit (e.g., hip flexing and knee extending simultaneously) while it's trying to contract forcefully. This creates enormous stress, making the long head the most commonly injured component of the hamstrings, with tears often occurring at its proximal musculotendinous junction near the ischial tuberosity.

In essence, the Long Head is the workhorse of the biceps femoris for powerful, coordinated movements involving the hip and knee, while the Short Head acts as a dedicated stabilizer and flexor of the knee.

Posterior thigh and popliteal fossa

 Hamstring muscles

 Biceps femoris

 Long head

 Short head

 Semitendinosus

 Semimembranosus

 Popliteal fossa

 Popliteal artery

 Popliteal vein

 Tibial nerve

 Common peroneal (fibular) nerve

 Small saphenous vein

 Popliteus muscle

Posterior thigh and popliteal fossa

 Hamstring muscles

 Biceps femoris

 Long head

 Short head

 Semitendinosus

 Semimembranosus

 Popliteal fossa

 Popliteal artery

 Popliteal vein

 Tibial nerve

 Common peroneal (fibular) nerve

 Small saphenous vein

 Popliteus muscle

Posterior thigh and popliteal fossa

 Hamstring muscles

 Biceps femoris

 Long head

 Short head

 Semitendinosus

 Semimembranosus

 Popliteal fossa

 Popliteal artery

 Popliteal vein

 Tibial nerve

 Common peroneal (fibular) nerve

 Small saphenous vein

 Popliteus muscle

Posterior thigh and popliteal fossa

 Hamstring muscles

 Biceps femoris

 Long head

 Short head

 Semitendinosus

 Semimembranosus

 Popliteal fossa

 Popliteal artery

 Popliteal vein

 Tibial nerve

 Common peroneal (fibular) nerve

 Small saphenous vein

 Popliteus muscle

Posterior thigh and popliteal fossa

 Hamstring muscles

 Biceps femoris

 Long head

 Short head

 Semitendinosus

 Semimembranosus

 Popliteal fossa

 Popliteal artery

 Popliteal vein

 Tibial nerve

 Common peroneal (fibular) nerve

 Small saphenous vein

 Popliteus muscle

Posterior thigh and popliteal fossa

 Hamstring muscles

 Biceps femoris

 Long head

 Short head

 Semitendinosus

 Semimembranosus

 Popliteal fossa

 Popliteal artery

 Popliteal vein

 Tibial nerve

 Common peroneal (fibular) nerve

 Small saphenous vein

 Popliteus muscle

Posterior thigh and popliteal fossa

 Hamstring muscles

 Biceps femoris

 Long head

 Short head

 Semitendinosus

 Semimembranosus

 Popliteal fossa

 Popliteal artery

 Popliteal vein

 Tibial nerve

 Common peroneal (fibular) nerve

 Small saphenous vein

 Popliteus muscle

Posterior thigh and popliteal fossa

 Hamstring muscles

 Biceps femoris

 Long head

 Short head

 Semitendinosus

 Semimembranosus

 Popliteal fossa

 Popliteal artery

 Popliteal vein

 Tibial nerve

 Common peroneal (fibular) nerve

 Small saphenous vein

 Popliteus muscle

Posterior thigh and popliteal fossa

 Hamstring muscles

 Biceps femoris

 Long head

 Short head

 Semitendinosus

 Semimembranosus

 Popliteal fossa

 Popliteal artery

 Popliteal vein

 Tibial nerve

 Common peroneal (fibular) nerve

 Small saphenous vein

 Popliteus muscle

Posterior thigh and popliteal fossa

 Hamstring muscles

 Biceps femoris

 Long head

 Short head

 Semitendinosus

 Semimembranosus

 Popliteal fossa

 Popliteal artery

 Popliteal vein

 Tibial nerve

 Common peroneal (fibular) nerve

 Small saphenous vein

 Popliteus muscle

Anteromedial thigh and knee

 Sartorius muscle

 Quadriceps femoris

 Rectus femoris

 Vastus lateralis

 Vastus medialis

 Vastus intermedius

 Iliopsoas muscle

 Gracilis

 Pectineus

 Adductor longus

 Obturator nerve

 Adductor brevis

 Adductor magnus

 Obturator externus

Anteromedial thigh and knee

 Sartorius muscle

 Quadriceps femoris

 Rectus femoris

 Vastus lateralis

 Vastus medialis

 Vastus intermedius

 Iliopsoas muscle

 Gracilis

 Pectineus

 Adductor longus

 Obturator nerve

 Adductor brevis

 Adductor magnus

 Obturator externus

Anteromedial thigh and knee

 Sartorius muscle

 Quadriceps femoris

 Rectus femoris

 Vastus lateralis

 Vastus medialis

 Vastus intermedius

 Iliopsoas muscle

 Gracilis

 Pectineus

 Adductor longus

 Obturator nerve

 Adductor brevis

 Adductor magnus

 Obturator externus

Anteromedial thigh and knee

 Sartorius muscle

 Quadriceps femoris

 Rectus femoris

 Vastus lateralis

 Vastus medialis

 Vastus intermedius

 Iliopsoas muscle

 Gracilis

 Pectineus

 Adductor longus

 Obturator nerve

 Adductor brevis

 Adductor magnus

 Obturator externus

Anteromedial thigh and knee

 Sartorius muscle

 Quadriceps femoris

 Rectus femoris

 Vastus lateralis

 Vastus medialis

 Vastus intermedius

 Iliopsoas muscle

 Gracilis

 Pectineus

 Adductor longus

 Obturator nerve

 Adductor brevis

 Adductor magnus

 Obturator externus

Anteromedial thigh and knee

 Sartorius muscle

 Quadriceps femoris

 Rectus femoris

 Vastus lateralis

 Vastus medialis

 Vastus intermedius

 Iliopsoas muscle

 Gracilis

 Pectineus

 Adductor longus

 Obturator nerve

 Adductor brevis

 Adductor magnus

 Obturator externus

Anteromedial thigh and knee

 Sartorius muscle

 Quadriceps femoris

 Rectus femoris

 Vastus lateralis

 Vastus medialis

 Vastus intermedius

 Iliopsoas muscle

 Gracilis

 Pectineus

 Adductor longus

 Obturator nerve

 Adductor brevis

 Adductor magnus

 Obturator externus

Anteromedial thigh and knee

 Sartorius muscle

 Quadriceps femoris

 Rectus femoris

 Vastus lateralis

 Vastus medialis

 Vastus intermedius

 Iliopsoas muscle

 Gracilis

 Pectineus

 Adductor longus

 Obturator nerve

 Adductor brevis

 Adductor magnus

 Obturator externus

Anteromedial thigh and knee

 Sartorius muscle

 Quadriceps femoris

 Rectus femoris

 Vastus lateralis

 Vastus medialis

 Vastus intermedius

 Iliopsoas muscle

 Gracilis

 Pectineus

 Adductor longus

 Obturator nerve

 Adductor brevis

 Adductor magnus

 Obturator externus

Anteromedial thigh and knee

 Sartorius muscle

 Quadriceps femoris

 Rectus femoris

 Vastus lateralis

 Vastus medialis

 Vastus intermedius

 Iliopsoas muscle

 Gracilis

 Pectineus

 Adductor longus

 Obturator nerve

 Adductor brevis

 Adductor magnus

 Obturator externus

Anteromedial thigh and knee

 Sartorius muscle

 Quadriceps femoris

 Rectus femoris

 Vastus lateralis

 Vastus medialis

 Vastus intermedius

 Iliopsoas muscle

 Gracilis

 Pectineus

 Adductor longus

 Obturator nerve

 Adductor brevis

 Adductor magnus

 Obturator externus

Anteromedial thigh and knee

 Sartorius muscle

 Quadriceps femoris

 Rectus femoris

 Vastus lateralis

 Vastus medialis

 Vastus intermedius

 Iliopsoas muscle

 Gracilis

 Pectineus

 Adductor longus

 Obturator nerve

 Adductor brevis

 Adductor magnus

 Obturator externus

Anteromedial thigh and knee

 Sartorius muscle

 Quadriceps femoris

 Rectus femoris

 Vastus lateralis

 Vastus medialis

 Vastus intermedius

 Iliopsoas muscle

 Gracilis

 Pectineus

 Adductor longus

 Obturator nerve

 Adductor brevis

 Adductor magnus

 Obturator externus

Anteromedial thigh and knee

 Sartorius muscle

 Quadriceps femoris

 Rectus femoris

 Vastus lateralis

 Vastus medialis

 Vastus intermedius

 Iliopsoas muscle

 Gracilis

 Pectineus

 Adductor longus

 Obturator nerve

 Adductor brevis

 Adductor magnus

 Obturator externus

Anteromedial thigh and knee

 Sartorius muscle

 Quadriceps femoris

 Rectus femoris

 Vastus lateralis

 Vastus medialis

 Vastus intermedius

 Iliopsoas muscle

 Gracilis

 Pectineus

 Adductor longus

 Obturator nerve

 Adductor brevis

 Adductor magnus

 Obturator externus

Femoral triangle

 Femoral triangle

 Femoral artery

 Profunda femoris artery

 Medial femoral circumflex

artery

 Lateral femoral circumflex

artery

 Femoral vein

 Femoral canal

 Femoral ring

 Femoral nerve

Femoral triangle

 Femoral triangle

 Femoral artery

 Profunda femoris artery

 Medial femoral circumflex

artery

 Lateral femoral circumflex

artery

 Femoral vein

 Femoral canal

 Femoral ring

 Femoral nerve

Femoral triangle

 Femoral triangle

 Femoral artery

 Profunda femoris artery

 Medial femoral circumflex

artery

 Lateral femoral circumflex

artery

 Femoral vein

 Femoral canal

 Femoral ring

 Femoral nerve

Femoral triangle

 Femoral triangle

 Femoral artery

 Profunda femoris artery

 Medial femoral circumflex

artery

 Lateral femoral circumflex

artery

 Femoral vein

 Femoral canal

 Femoral ring

 Femoral nerve

Femoral triangle

 Femoral triangle

 Femoral artery

 Profunda femoris artery

 Medial femoral circumflex

artery

 Lateral femoral circumflex

artery

 Femoral vein

 Femoral canal

 Femoral ring

 Femoral nerve

Femoral triangle

 Femoral triangle

 Femoral artery

 Profunda femoris artery

 Medial femoral circumflex

artery

 Lateral femoral circumflex

artery

 Femoral vein

 Femoral canal

 Femoral ring

 Femoral nerve

Femoral triangle

 Femoral triangle

 Femoral artery

 Profunda femoris artery

 Medial femoral circumflex

artery

 Lateral femoral circumflex

artery

 Femoral vein

 Femoral canal

 Femoral ring

 Femoral nerve

Femoral triangle

 Femoral triangle

 Femoral artery

 Profunda femoris artery

 Medial femoral circumflex

artery

 Lateral femoral circumflex

artery

 Femoral vein

 Femoral canal

 Femoral ring

 Femoral nerve

Femoral triangle

 Femoral triangle

 Femoral artery

 Profunda femoris artery

 Medial femoral circumflex

artery

 Lateral femoral circumflex

artery

 Femoral vein

 Femoral canal

 Femoral ring

 Femoral nerve

Femoral triangle

 Femoral triangle

 Femoral artery

 Profunda femoris artery

 Medial femoral circumflex

artery

 Lateral femoral circumflex

artery

 Femoral vein

 Femoral canal

 Femoral ring

 Femoral nerve

Adductor canal of Hunter (subsartorial canal)

 Adductor canal

 Adductor hiatus

 Popliteal artery

 Popliteal vein

 Saphenous nerve

 Great saphenous vein

Adductor canal of Hunter (subsartorial canal)

 Adductor canal

 Adductor hiatus

 Popliteal artery

 Popliteal vein

 Saphenous nerve

 Great saphenous vein

Adductor canal of Hunter (subsartorial canal)

 Adductor canal

 Adductor hiatus

 Popliteal artery

 Popliteal vein

 Saphenous nerve

 Great saphenous vein

Adductor canal of Hunter (subsartorial canal)

 Adductor canal

 Adductor hiatus

 Popliteal artery

 Popliteal vein

 Saphenous nerve

 Great saphenous vein

Adductor canal of Hunter (subsartorial canal)

 Adductor canal

 Adductor hiatus

 Popliteal artery

 Popliteal vein

 Saphenous nerve

 Great saphenous vein

Adductor canal of Hunter (subsartorial canal)

 Adductor canal

 Adductor hiatus

 Popliteal artery

 Popliteal vein

 Saphenous nerve

 Great saphenous vein

Adductor canal of Hunter (subsartorial canal)

 Adductor canal

 Adductor hiatus

 Popliteal artery

 Popliteal vein

 Saphenous nerve

 Great saphenous vein

Knee

 Patella

 Ligaments

 Tibial (medial) collateral ligament

 Fibular (lateral) collateral ligament

 Anterior cruciate ligament

 Posterior cruciate ligament

 Ligamentum patellae

 Subcutaneous prepatellar bursa

 Suprapatellar bursa

 Menisci (medial and lateral)

 Semilunar cartilage

 Fibrous capsule of humeroulnar joint

 Iliofemoral ligament

 Ischiofemoral ligament

 Ligament of head of femur (teres)

 Lunate articular surface

 Synovial membrane of hip joint

 Synovial membrane of knee joint

Knee

 Patella

 Ligaments

 Tibial (medial) collateral ligament

 Fibular (lateral) collateral ligament

 Anterior cruciate ligament

 Posterior cruciate ligament

 Ligamentum patellae

 Subcutaneous prepatellar bursa

 Suprapatellar bursa

 Menisci (medial and lateral)

 Semilunar cartilage

 Fibrous capsule of humeroulnar joint

 Iliofemoral ligament

 Ischiofemoral ligament

 Ligament of head of femur (teres)

 Lunate articular surface

 Synovial membrane of hip joint

 Synovial membrane of knee joint

Knee

 Patella

 Ligaments

 Tibial (medial) collateral ligament

 Fibular (lateral) collateral ligament

 Anterior cruciate ligament

 Posterior cruciate ligament

 Ligamentum patellae

 Subcutaneous prepatellar bursa

 Suprapatellar bursa

 Menisci (medial and lateral)

 Semilunar cartilage

 Fibrous capsule of humeroulnar joint

 Iliofemoral ligament

 Ischiofemoral ligament

 Ligament of head of femur (teres)

 Lunate articular surface

 Synovial membrane of hip joint

 Synovial membrane of knee joint

Knee

 Patella

 Ligaments

 Tibial (medial) collateral ligament

 Fibular (lateral) collateral ligament

 Anterior cruciate ligament

 Posterior cruciate ligament

 Ligamentum patellae

 Subcutaneous prepatellar bursa

 Suprapatellar bursa

 Menisci (medial and lateral)

 Semilunar cartilage

 Fibrous capsule of humeroulnar joint

 Iliofemoral ligament

 Ischiofemoral ligament

 Ligament of head of femur (teres)

 Lunate articular surface

 Synovial membrane of hip joint

 Synovial membrane of knee joint

Knee

 Patella

 Ligaments

 Tibial (medial) collateral ligament

 Fibular (lateral) collateral ligament

 Anterior cruciate ligament

 Posterior cruciate ligament

 Ligamentum patellae

 Subcutaneous prepatellar bursa

 Suprapatellar bursa

 Menisci (medial and lateral)

 Semilunar cartilage

 Fibrous capsule of humeroulnar joint

 Iliofemoral ligament

 Ischiofemoral ligament

 Ligament of head of femur (teres)

 Lunate articular surface

 Synovial membrane of hip joint

 Synovial membrane of knee joint

Knee

 Patella

 Ligaments

 Tibial (medial) collateral ligament

 Fibular (lateral) collateral ligament

 Anterior cruciate ligament

 Posterior cruciate ligament

 Ligamentum patellae

 Subcutaneous prepatellar bursa

 Suprapatellar bursa

 Menisci (medial and lateral)

 Semilunar cartilage

 Fibrous capsule of humeroulnar joint

 Iliofemoral ligament

 Ischiofemoral ligament

 Ligament of head of femur (teres)

 Lunate articular surface

 Synovial membrane of hip joint

 Synovial membrane of knee joint

Knee

 Patella

 Ligaments

 Tibial (medial) collateral ligament

 Fibular (lateral) collateral ligament

 Anterior cruciate ligament

 Posterior cruciate ligament

 Ligamentum patellae

 Subcutaneous prepatellar bursa

 Suprapatellar bursa

 Menisci (medial and lateral)

 Semilunar cartilage

 Fibrous capsule of humeroulnar joint

 Iliofemoral ligament

 Ischiofemoral ligament

 Ligament of head of femur (teres)

 Lunate articular surface

 Synovial membrane of hip joint

 Synovial membrane of knee joint

Knee

 Patella

 Ligaments

 Tibial (medial) collateral ligament

 Fibular (lateral) collateral ligament

 Anterior cruciate ligament

 Posterior cruciate ligament

 Ligamentum patellae

 Subcutaneous prepatellar bursa

 Suprapatellar bursa

 Menisci (medial and lateral)

 Semilunar cartilage

 Fibrous capsule of humeroulnar joint

 Iliofemoral ligament

 Ischiofemoral ligament

 Ligament of head of femur (teres)

 Lunate articular surface

 Synovial membrane of hip joint

 Synovial membrane of knee joint

Knee

 Patella

 Ligaments

 Tibial (medial) collateral ligament

 Fibular (lateral) collateral ligament

 Anterior cruciate ligament

 Posterior cruciate ligament

 Ligamentum patellae

 Subcutaneous prepatellar bursa

 Suprapatellar bursa

 Menisci (medial and lateral)

 Semilunar cartilage

 Fibrous capsule of humeroulnar joint

 Iliofemoral ligament

 Ischiofemoral ligament

 Ligament of head of femur (teres)

 Lunate articular surface

 Synovial membrane of hip joint

 Synovial membrane of knee joint

Knee

 Patella

 Ligaments

 Tibial (medial) collateral ligament

 Fibular (lateral) collateral ligament

 Anterior cruciate ligament

 Posterior cruciate ligament

 Ligamentum patellae

 Subcutaneous prepatellar bursa

 Suprapatellar bursa

 Menisci (medial and lateral)

 Semilunar cartilage

 Fibrous capsule of humeroulnar joint

 Iliofemoral ligament

 Ischiofemoral ligament

 Ligament of head of femur (teres)

 Lunate articular surface

 Synovial membrane of hip joint

 Synovial membrane of knee joint

Knee

 Patella

 Ligaments

 Tibial (medial) collateral ligament

 Fibular (lateral) collateral ligament

 Anterior cruciate ligament

 Posterior cruciate ligament

 Ligamentum patellae

 Subcutaneous prepatellar bursa

 Suprapatellar bursa

 Menisci (medial and lateral)

 Semilunar cartilage

 Fibrous capsule of humeroulnar joint

 Iliofemoral ligament

 Ischiofemoral ligament

 Ligament of head of femur (teres)

 Lunate articular surface

 Synovial membrane of hip joint

 Synovial membrane of knee joint

Knee

 Patella

 Ligaments

 Tibial (medial) collateral ligament

 Fibular (lateral) collateral ligament

 Anterior cruciate ligament

 Posterior cruciate ligament

 Ligamentum patellae

 Subcutaneous prepatellar bursa

 Suprapatellar bursa

 Menisci (medial and lateral)

 Semilunar cartilage

 Fibrous capsule of humeroulnar joint

 Iliofemoral ligament

 Ischiofemoral ligament

 Ligament of head of femur (teres)

 Lunate articular surface

 Synovial membrane of hip joint

 Synovial membrane of knee joint

Knee

 Patella

 Ligaments

 Tibial (medial) collateral ligament

 Fibular (lateral) collateral ligament

 Anterior cruciate ligament

 Posterior cruciate ligament

 Ligamentum patellae

 Subcutaneous prepatellar bursa

 Suprapatellar bursa

 Menisci (medial and lateral)

 Semilunar cartilage

 Fibrous capsule of humeroulnar joint

 Iliofemoral ligament

 Ischiofemoral ligament

 Ligament of head of femur (teres)

 Lunate articular surface

 Synovial membrane of hip joint

 Synovial membrane of knee joint

Knee

 Patella

 Ligaments

 Tibial (medial) collateral ligament

 Fibular (lateral) collateral ligament

 Anterior cruciate ligament

 Posterior cruciate ligament

 Ligamentum patellae

 Subcutaneous prepatellar bursa

 Suprapatellar bursa

 Menisci (medial and lateral)

 Semilunar cartilage

 Fibrous capsule of humeroulnar joint

 Iliofemoral ligament

 Ischiofemoral ligament

 Ligament of head of femur (teres)

 Lunate articular surface

 Synovial membrane of hip joint

 Synovial membrane of knee joint

Knee

 Patella

 Ligaments

 Tibial (medial) collateral ligament

 Fibular (lateral) collateral ligament

 Anterior cruciate ligament

 Posterior cruciate ligament

 Ligamentum patellae

 Subcutaneous prepatellar bursa

 Suprapatellar bursa

 Menisci (medial and lateral)

 Semilunar cartilage

 Fibrous capsule of humeroulnar joint

 Iliofemoral ligament

 Ischiofemoral ligament

 Ligament of head of femur (teres)

 Lunate articular surface

 Synovial membrane of hip joint

 Synovial membrane of knee joint

Knee

 Patella

 Ligaments

 Tibial (medial) collateral ligament

 Fibular (lateral) collateral ligament

 Anterior cruciate ligament

 Posterior cruciate ligament

 Ligamentum patellae

 Subcutaneous prepatellar bursa

 Suprapatellar bursa

 Menisci (medial and lateral)

 Semilunar cartilage

 Fibrous capsule of humeroulnar joint

 Iliofemoral ligament

 Ischiofemoral ligament

 Ligament of head of femur (teres)

 Lunate articular surface

 Synovial membrane of hip joint

 Synovial membrane of knee joint

Knee

 Patella

 Ligaments

 Tibial (medial) collateral ligament

 Fibular (lateral) collateral ligament

 Anterior cruciate ligament

 Posterior cruciate ligament

 Ligamentum patellae

 Subcutaneous prepatellar bursa

 Suprapatellar bursa

 Menisci (medial and lateral)

 Semilunar cartilage

 Fibrous capsule of humeroulnar joint

 Iliofemoral ligament

 Ischiofemoral ligament

 Ligament of head of femur (teres)

 Lunate articular surface

 Synovial membrane of hip joint

 Synovial membrane of knee joint

Knee

 Patella

 Ligaments

 Tibial (medial) collateral ligament

 Fibular (lateral) collateral ligament

 Anterior cruciate ligament

 Posterior cruciate ligament

 Ligamentum patellae

 Subcutaneous prepatellar bursa

 Suprapatellar bursa

 Menisci (medial and lateral)

 Semilunar cartilage

 Fibrous capsule of humeroulnar joint

 Iliofemoral ligament

 Ischiofemoral ligament

 Ligament of head of femur (teres)

 Lunate articular surface

 Synovial membrane of hip joint

 Synovial membrane of knee joint

Knee

 Patella

 Ligaments

 Tibial (medial) collateral ligament

 Fibular (lateral) collateral ligament

 Anterior cruciate ligament

 Posterior cruciate ligament

 Ligamentum patellae

 Subcutaneous prepatellar bursa

 Suprapatellar bursa

 Menisci (medial and lateral)

 Semilunar cartilage

 Fibrous capsule of humeroulnar joint

 Iliofemoral ligament

 Ischiofemoral ligament

 Ligament of head of femur (teres)

 Lunate articular surface

 Synovial membrane of hip joint

 Synovial membrane of knee joint