Muscles of the Lower Limbs

Iliopsoas Muscle: These are the primary hip flexors, vital for actions such as walking and running. It is made up of two muscles. They are:

  • Iliacus: Originates broadly from the iliac fossa of the pelvis and attaches to the lesser trochanter of the femur, playing a significant role in flexing the thigh at the hip joint.

  • Psoas Major: Originates from the lumbar vertebrae, traversing across the pelvis to insert into the femur. Psoas major joins the ilacus muscle at its insertion in the femur. It is key for hip flexion and stabilizing the lumbar spine.

Psoas Minor: A smaller muscle often absent in individuals, it assists in spinal flexion and is not a major hip flexor but contributes to overall pelvic stability. It connects the lumbar vertebrae to the pubis in the hip bone.

Gluteal Muscles: These muscles are pivotal for hip movement and stability during various activities.

  • Gluteus Maximus: The largest muscle in the human, it is crucial for hip extension, lateral rotation, and maintaining erect posture. It also plays a role in climbing stairs and standing up from a sitting position. It originates from the gluteus surface of the ilium (posterior gluteal line of the ilium) and insert into the gluteal tuberosity of the femur and the iliotibial tract, providing powerful leverage during movements such as walking, running, and jumping.

  • Gluteus Medius: Situated below the gluetus maximus and above gluteus minimus, it is responsible for hip stabilization during activities like walking and running by preventing pelvic tilt. Gluteus medius originates from the back side of ilium and inserts onto the lateral side of greater trochanter of the femur.

  • Gluteus Minimus: The smallest of the gluteal muscles, it assists in hip abduction and medial rotation of the thigh, contributing to overall hip stability.

  • Tensor Fasciae Latae (TFL): This muscle helps in stabilizing the hip and knee through its connection with the iliotibial band. It originates from the anterior superior iliac spine as well as the anterior aspect of the iliac aspect. It inserts into iliotibial tract.

Smaller Hip Muscles (From superior to inferior):

  • Piriformis: Located directly inferiorthe gluteus minimus, it is important for hip external rotation, stretching the piriformis can alleviate sciatic pain, often correlated with the pigeon pose in yoga.

  • Gemellus Superior/Inferior: Paired muscles that function together in external rotation and stability of the hip joint. Gemellus superior originates from the ischial spine and inserts into the upper part of the greater trochanter

  • Obturator Internus: Located between gemellus superior and gemellus inferior, it originates from posterior surface of the obturator membrane and inserts into medial surface of the greater trochanter of femur. Obturator internus contributes to external rotation and stabilization of the hip.

  • Obturator externus: A muscle that lies deep to the quadratus femoris, it originates from the external surface of the obturator membrane and rami of pubis bone and ischium, inserting also into the greater trochanter, and it plays a key role in the external rotation of the hip joint.

  • Quadratus Femoris: A square-shaped muscle beneath the others, it plays a key role in external rotation of the thigh. It attaches onto the intertrochanteric crest of the femur and assists in providing both stability and movement during various hip activities.

Q) Which muscles inserts into the greater trochanter of the femur?

A) The muscles that insert into the greater trochanter of the femur include:

  • Piriformis

  • Gluteus minimus

  • Gluteus medius

  • Obturator Internus

  • Obturator Externus

  • Quadratus Femoris

Thigh Muscles

  • Sartorius: The longest muscle in the body, running from the anterior superior iliac spine (ASIS) to the medial aspect of the tibia. It is involved in hip flexion, external rotation, and abduction, performing movements essential in activities like sitting cross-legged.

  • Quadriceps: This muscle group is crucial for knee extension and engages in various daily activities such as walking and running. They all insert into the patellar tendon.

    • Vastus Lateralis, Vastus Intermedius, Vastus Medialis: They originate from different parts of the femur to contribute to the quadriceps, primarily responsible for knee extension.

    • Rectus Femoris: Although it is a part of the quadriceps group, it crosses both the hip and knee joints. Remembering "rectus" for straightness may help in recalling its role in both hip flexion and knee extension.

Hamstrings: Comprising three muscles located on the back of the thigh, instrumental in knee flexion and hip extension.

  • Biceps Femoris: Has two heads, contributing to knee flexion and hip extension, originating from the ischial tuberosity (long head) and the femur (short head).

  • Semitendinosus: Located more medial to the biceps femoris, its known for its long tendon and involvement in knee flexion, it also assists in medial rotation of the thigh. It originates from the lateral angle of ischial tuberosity between biceps femoris and semimembranosus and inserts on the medial aspect of the tibia.

  • Semimembranosus: This muscle presents a wider appearance and is situated more medially, assisting with knee flexion and providing medial rotation of the thigh.

Adductor Group (Five muscles are involved in hip adduction): Critical for stabilizing the pelvis and controlling the movement of the leg during locomotion.

  • Adductor Magnus, Adductor Longus, Adductor Brevis: Use the MLB mnemonic corresponding to size to remember them (Magnus being the largest, followed by Longus, and then Brevis).

  • Gracilis: A long, thin muscle that assists in adducting the thigh and helps with knee flexion.

  • Pectineus: The most superior of the adductor muscles, connecting the pubis to the femur. It originates from the pectineal line of pubis on the superior pubic ramus. The pectineus inserts into pectineal line of the femur. It is innervated by the femoral nerve and occasionally by the accessory obturator nerve.

Lower Leg Muscles

Anterior Muscles

These muscles cross in front of the ankles. Therefore, they are involved in dorsiflexion of the foot.

  • Tibialis Anterior: Positioned at the front of the tibia, it is innervated by the deep fibular nerve.

  • Extensor Digitorum Longus: Responsible for extending the toes and plays a vital role in the push-off phase of walking.

  • Extensor Hallucis Longus: Specifically extends the big toe (hallus).

  • Fibularis Tertius: A smaller muscle, it connects the distal part of the fibula to the metatarsal. It originates from the interosseus membrane on the lower third of the fibula and inserts into dorsal surface of the fifth metatarsal, aiding in eversion of the foot. Fibularis tertius is innervated by the deep fibular nerve.

Lateral Muscles

  • Fibularis Longus: Responsible for ankle eversion, it provides stability to the lateral side of the ankle.

  • Fibularis Brevis: Similar to the longus but shorter, also aids in eversion, helping ensure balance during dynamic movements.

Q) Name the Fibularis muscles

A)

  1. Fibularis longus

  2. Fibularis brevis

  3. Fibularis tertius

Posterior Muscles

Gastrocnemius and soleus share the Achilles tendon.

Gastrocnemius

  • It is a three joint muscle that crosses the knee, talocrural and subtalar joints.

  • Gastrocnemius muscle has two heads: Medial and lateral head. The medial head originates from the posterior aspect of the femur above the medial condyle, while the lateral head originates from the posterior aspect of the femur above the lateral condyle. They form the definitive shape of the calf.

  • The bulk of the gastrocnemius muscle from each of the heads comes together and insert into the posterior surface of a broad membranous tendon.

  • The upper part of the tendocalcaneous is formed as a result of the merging of the broad membranous tendon with the soleus tendon, creating a strong structure that connects to the calcaneus (heel bone).

  • Tendocalcaneous narrows down until it reaches the calcaneus, where it expands for its insertion into the posterior part of the calcaneus.

  • Gastrocnemius is innervated by the tibial nerve (S1 and S2 nerve root).

  • Its main function is to facilitate plantar flexion of the foot at the ankle joint, enabling movements such as walking, running, and jumping. Additionally, it assists in flexing the knee joint due to its dual origin from the femur.

Soleus

  • Positioned deep to the gastrocnemius, it is crucial for stabilizing the ankle during activities like running and standing.

  • It is innervated by the tibial nerve.

  • The soleus muscle originates from the posterior surface of the tibia and the fibula, specifically the soleal line of the tibia and the head of the fibula.

  • It inserts into the posterior surface of the calcaneus through the Achilles tendon (tendocalcaneus).

Plantaris: A small muscle that assists in plantar flexion but is often considered a vestigial muscle.

Popliteus: A unique muscle that internal rotation of the femur on the tibia, commonly referred to as unlocking the knee.

Q) Which muscles form the triceps surae?

A) The triceps surae is comprised of the gastrocnemius, plantaris and the soleus muscle.

Tarsal Tunnel Muscles (Mnemonic: Tom, Dick, and Harry)

Tibialis Posterior, Flexor Digitorum Longus and Flexor Hallucis Longus play an essential role in inversion and stability of the foot.

Tibialis Posterior

The primary muscle responsible for plantar flexion and inversion of the foot, assisting in maintaining the medial arch. It is innervated by the tibial nerve, which provides both motor and sensory innervation to the muscles in the posterior compartment of the leg.

It originates from the posterior aspect of the tibia, fibula, and interosseous membrane and inserts into, the navicular bone and the medial cuneiform, as well as the bases of the second, third, and fourth metatarsals.

Flexor digitorum longus: A muscle that flexes the lateral four toes and assists in plantar flexion of the foot, innervated by the tibial nerve. It originates from the posterior surface of the tibia and inserts into the distal phalanges of the second to fifth toes.

Flexor hallucis longus: A muscle that flexes the big toe and plays a role in plantar flexion of the foot, also innervated by the tibial nerve. It originates from the posterior fibula and the interosseous membrane and inserts into the distal phalanx of the big toe.

Foot Muscles

Muscles are organized into layers for dissection, with each layer corresponding to distinct functional roles in foot movement and stability.

Arches of Foot: Longitudinal and transverse arches. They are critical for load distribution and maintaining posture during movement. Transverse arch cuts across the metatarsal.

Dorsal Muscles

  • Extensor Digitorum Brevis: Slightly different from the longus, it extends the toes and originates directly from the foot. It inserts into the proximal phalanges of the toes.

  • Extensor Hallucis Brevis: Extensor Hallucis brevis inserts into and extends the big toe. It is innervated by the deep peroneal nerve, which also supplies the extensor muscles in the anterior compartment of the leg.

  • Dorsal interossei is found on top of the foot. It abducts the metatarsal.

Plantar Muscles

  • Plantar interossei adducts the metatarsal.

  • Abductor Hallucis: Abducts the big toe, important for maintaining balance and foot structure.

  • Adductor Hallucis: Stabilizes the arches as it pulls the big toe medially. It spans across the metatarsals.

  • Abductor Digiti Minimi: This muscle inserts into and abducts the pinky toe. It also supports the longitudinal arch of the foot.

  • Flexor Digitorum Brevis: Flexes the four smaller toes. It supports the longitudinal arch. It originates from the calcaneus and the plantar aponeurosis, attaching to the middle phalanges of the lesser toes. It is innervated by the medial plantar nerve, which arises from the tibial nerve.

Deep foot muscles

They function collectively to flex and accommodate the toes’ movements, paralleling the function of the hand's lumbricals but adapted for foot mechanics.

Quadratus Plantae: It is a square shaped muscle on the plantar aspect of the foot. It originates from the calcaneus and inserts into the tendons of the flexor digitorum longus, aiding in toe flexion and alignment through its unique attachment. The muscle is innervated by the lateral plantar nerve.

Flexor Hallucis Brevis: This small muscle is located on the plantar side of the foot and is responsible for flexing the big toe. It originates from the cuboid and the lateral cuneiform bones, inserting into the base of the proximal phalanx of the hallux. The Flexor Hallucis Brevis is innervated by the medial plantar nerve. It bends the metatarsophalangeal joint.

Flexor Digiti Minimi Brevis: This muscle functions to flex the little toe. It arises from the fifth metatarsal bone and inserts into the base of the proximal phalanx of the fifth digit. The Flexor Digiti Minimi Brevis is innervated by the lateral plantar nerve, assisting in the movement of the metatarsophalangeal joint.

Lumbricals of the foot are a set of four muscles that originate from the tendons of the flexor digitorum longus. They insert into the extensor expansions of the digits and are responsible for flexing the metatarsophalangeal joints while extending the interphalangeal joints.