Anterior Thigh Muscles

EXTREMITY ANATOMY

Lower Limb Cutaneous Nerves and Anterior Thigh Muscles

Lower Limb Lymphatics

Superficial Lymphatics

  • Plexus on the plantar surface.

  • Superficial lymphatic vessels accompany the saphenous veins:

    • Great saphenous vein

    • Small saphenous vein

  • Superficial lymphatics end at the superficial inguinal nodes. Most of this lymph drains to the external iliac nodes, while some drains to the deep inguinal nodes.

  • Small saphenous lymphatics drain to the popliteal nodes.

Superficial Inguinal Nodes

  • Quantity: 12-20 nodes.

  • Orientation:

    • Horizontal Group: Located along the inguinal ligament.

    • Receives drainage from:

      • Abdominal wall

      • Buttock

      • Penis

      • Scrotum

      • Perineum

    • Projects to external iliac nodes.

    • Vertical Group: Located along the greater saphenous vein.

    • Receives drainage from the lower limb.

    • Projects to external iliac nodes.

Deep Inguinal Nodes

  • Quantity: 1-3 nodes.

  • Location: Medial side of the femoral vein.

  • Receives drainage from:

    • Popliteal nodes

    • Deeper drainage

  • Projects to external iliac nodes.

Popliteal Nodes

  • Quantity: 6-7 nodes.

  • Location: In the popliteal fossa.

  • Projects to deep inguinal nodes.

Cutaneous Innervation

Cluneal Nerves

  • Superior cluneal nerve:

    • Origin: L1-3.

    • Innervation: Gluteal region to greater trochanter.

  • Middle cluneal nerve:

    • Origin: S1-3.

    • Innervation: Sacral area.

  • Inferior cluneal nerve:

    • Origin: S1-3.

    • Innervation: Lower buttock, branch of posterior femoral nerve.

Femoral Nerves Distribution

  • Anterior femoral cutaneous nerve:

    • Origin: L2-3.

    • Innervation: Distal ¾ of anterior and medial thigh.

  • Femoral branch of genitofemoral nerve:

    • Origin: L1-2.

    • Innervation: Proximal ¼ of anterior thigh.

  • Lateral femoral cutaneous nerve:

    • Origin: L2-3.

    • Innervation:

    • Anterior branch: Lateral thigh.

    • Posterior branch: Lateral buttock.

Posterior Thigh Innervation

  • Posterior femoral cutaneous nerve:

    • Origin: S1-3.

    • Innervation: Posterior thigh, inferior buttock.

  • Cutaneous branch of obturator nerve:

    • Origin: L2-4.

    • Innervation: Proximal 1/3 of medial thigh.

  • Saphenous nerve:

    • Origin: L3-4 (branch of femoral nerve).

    • Innervation: Anterior and medial leg, posterior half and medial foot.

Lower Leg Cutaneous Innervation

  • Lateral sural nerve:

    • Origin: L5-S2.

    • Innervation: Posterior proximal 2/3 of the leg.

  • Medial sural nerve:

    • Origin: S1-2 (from tibial nerve).

    • Innervation: Heel.

  • Sural nerve:

    • Origin: S1-2 (union of lateral and medial sural nerves).

    • Innervation: Lateral foot; runs with lesser saphenous vein.

Foot Innervation

  • Superficial peroneal nerve:

    • Origin: L4-S1 (from common peroneal nerve).

    • Innervation: Distal 1/3 of leg, dorsum of foot.

  • Medial plantar nerve:

    • Origin: L4-5.

    • Innervation: Medial plantar foot.

  • Lateral plantar nerve:

    • Origin: S1-2.

    • Innervation: Lateral plantar foot.

  • Lateral calcaneal nerve:

    • Origin: S1-2 (from sural nerve).

    • Innervation: Heel.

  • Medial calcaneal nerve:

    • Origin: S1-2 (from tibial nerve).

    • Innervation: Heel.

Dermatomes

  • Overview: Except for some proximal branches of T12 & L1, sensory input comes from the lumbar and sacral plexus.

  • Dermatome Function: Reflects the developmental rotation of the lower limb.

Anterior Thigh

Thigh Muscles

  • Muscles involved in the movement of the thigh can be grouped into four compartments:

    • Anterior Compartment:

    • Primary Function: Flex the thigh (femur), extend the leg.

    • Innervation: Femoral nerve.

    • Medial Compartment:

    • Primary Function: Adduct the thigh.

    • Innervation: Obturator nerve.

    • Posterior Compartment:

    • Primary Function: Extend the thigh, flex the leg.

    • Innervation: Tibial portion of the sciatic nerve.

    • Lateral Compartment:

    • Primary Function: Abduct the thigh.

    • Muscles migrated slightly posteriorly and superiorly to form the gluteal muscles, which act as major thigh extensors.

Iliopsoas Muscle Complex

Psoas Muscle

  • Description: The strongest hip (thigh, femur) flexor with the widest range of motion.

  • Origin: Arises from the transverse processes & bodies of T12 – L5 vertebrae.

  • Insertion: Tapers inferiorly crossing anterior to the sacrum and SI joint to join with the iliacus, inserting on the lesser trochanter of the femur.

  • Action:

    • Flexes the thigh.

    • Flexes the trunk.

    • Lateral lumbar spine flexor.

    • Major postural muscle, active in gait performing an eccentric contraction to resist acceleration due to gravity.

  • Innervation: Ventral rami of L1-3.

  • Note: In ~1/2 of people, a psoas minor is present on the anterior surface of the psoas.

Iliacus Muscle

  • Description: Works in concert with the psoas muscle and plays a major role in trunk stability and posture.

  • Origin: Arises from the inner surface of the ala of the ilium (iliac fossa).

  • Insertion: Fibers blend with the psoas and insert on the lesser trochanter of the femur.

  • Innervation: Femoral nerve.

Sartorius

  • Description: Known as the tailor’s muscle; the longest muscle in the body. This muscle crosses both the hip and knee joints from lateral to medial.

  • Origin: Anterior superior iliac spine.

  • Insertion: Superior portion of the medial surface of the tibia, close to the insertion of the gracilis & semitendinosus.

  • Action:

    • Flexion, abduction, and lateral rotation of the thigh at the hip.

    • Flexes the leg at the knee.

    • Stabilizes the pelvis.

  • Functionality: Serves as a synergist in all its functions despite being smaller compared to other anterior thigh muscles.

Quadriceps Muscle

  • Description: Main bulk of the anterior thigh musculature; major leg extender also capable of flexing the hip. Crucial in activities such as rising from a chair, climbing, and walking, especially downhill.

Rectus Femoris

  • Origin: Has two separate heads:

    • Straight head: Anterior inferior iliac spine.

    • Reflected head: From the ilium just superior to the acetabulum.

  • Insertion: Base of the patella.

  • Action:

    • Extends knee.

    • Flexes the thigh at the hip.

  • Innervation: Femoral nerve.

  • Note: Only quadriceps muscle that crosses the hip joint.

Vastus Medialis

  • Origin: Arises from the intertrochanteric line and medial lip of the linea aspera, and medial intermuscular septum.

  • Insertion: Inserts on the medial border of the quadriceps tendon. Some inferior fibers insert directly into the medial side of the patella.

  • Action: Extends leg at the knee.

  • Innervation: Femoral nerve.

  • Note: The three vasti muscles contribute some aponeurotic fibers to the joint capsule of the knee.

Vastus Intermedius

  • Origin: Arises from the anterior & lateral aspects of the femoral shaft and the lateral intermuscular septum.

  • Insertion: The posterior surface of the base of the patella, forming part of the quadriceps tendon.

  • Action: Extends the leg at the knee.

  • Innervation: Femoral nerve.

Vastus Lateralis

  • Origin: Arises from the posterior aspect of the femur at the greater trochanter, continuing inferiorly along the lateral lip of the linea aspera.

  • Insertion: Most of the muscle inserts into the lateral patella and quadriceps tendon (with the rectus tendon), also attaches to the tibia and patella via an aponeurosis.

  • Action: Extends the leg at the knee, supports knee joint.

  • Innervation: Femoral nerve.

Musculus Articularis

  • Description: Articular muscle of the knee (musculus articularis genus).

  • Origin: Formed by small flat slips of muscle from the vastus intermedius muscle distally.

  • Insertion: Attaches to the synovial membrane of the knee joint & suprapatellar bursa.

  • Anatomy: Comprises a variable number of muscle bundles (1-7) originating from below the distal 1/5th of the anterior femur.

  • Function: Distracts the synovial membrane, preventing folds of the membrane from being compressed between the femur and the patella.

  • Innervation: Femoral nerve.

Summary of Origins & Insertions of the Anterior Thigh Muscles

  • Iliacus

  • Sartorius

  • Rectus femoris (including straight and reflected head)

  • Pectineus

  • Vastus Lateralis

  • Vastus Medialis

  • Vastus Intermedius

  • Articular Muscle of the Knee

  • Identification of flexors of hip and extensors of knee.