Comprehensive Myology of the Lower Limb: Attachments, Actions, and Neurovascular Supply

Posterior Thigh Compartment

Semitendinosus

• Proximal Attachment: Ischial tuberosity.

• Distal Attachment: Pes anserine (superior medial tibia).

• Action: Extends thigh; flexes leg; medially rotates leg when leg is flexed. When hip and knee joints are flexed, these muscles can extend the trunk at the hip joint.

• Innervation: Tibial division of sciatic nerve ($L5$-$S2$).

• Artery: Deep Femoral artery (and perforating branches).

Semimembranosus

• Proximal Attachment: Ischial tuberosity.

• Distal Attachment: Posterior medial condyle of tibia.

• Action: Extends thigh; flexes leg; medially rotates leg when leg is flexed. When hip and knee joints are flexed, these muscles can extend the trunk at the hip joint.

• Innervation: Tibial division of sciatic nerve ($L5$-$S2$).

• Artery: Deep Femoral artery (and perforating branches).

Biceps Femoris

• Proximal Attachment:

  • Long head: Ischial tuberosity.

  • Short head: Lateral lip of linea aspera and lateral supracondylar line of femur.

• Distal Attachment: Lateral side of the head of the fibula.

• Action: Flexes leg and laterally rotates leg when flexed. The long head specifically extends the thigh.

• Innervation:

  • Long Head: Tibial division of sciatic nerve ($L5$-$S2$).

  • Short Head: Common fibular division of sciatic nerve ($L5$-$S2$).

• Artery: Deep Femoral artery (and perforating branches).

Gluteal Region

Gluteus Maximus

• Proximal Attachment: Ilium posterior to the posterior gluteal line; posterior surface of the sacrum and coccyx; sacrotuberous ligament.

• Distal Attachment: Iliotibial tract (inserts into the lateral condyle of the tibia at Gerdy's tubercle); gluteal tuberosity of the femur.

• Action: Extends thigh between flexed and standing positions; assists in external rotation (ER) of the thigh; fixes the hip joint and assists in rising from a sitting position. Upper fibers abduct the thigh, while lower fibers adduct the thigh.

• Innervation: Inferior gluteal nerve ($L5$-$S2$).

• Artery: Inferior gluteal artery.

Gluteus Medius

• Proximal Attachment: Between anterior and posterior gluteal lines.

• Distal Attachment: Lateral surface of the greater trochanter.

• Action: Abducts thigh; keeps the pelvis level when the opposite limb is elevated. Anterior fibers medially rotate the thigh; posterior fibers laterally rotate the thigh.

• Innervation: Superior gluteal nerve ($L4$-$S1$).

• Artery: Superior gluteal artery.

Gluteus Minimus

• Proximal Attachment: Between anterior and inferior gluteal lines.

• Distal Attachment: Anterior surface of the greater trochanter.

• Action: Abducts thigh; keeps the pelvis level when the opposite limb is elevated. Medially rotates the thigh.

• Innervation: Superior gluteal nerve ($L4$-$S1$).

• Artery: Superior gluteal artery.

Tensor Fasciae Latae (TFL)

• Proximal Attachment: Anterior superior iliac spine (ASIS); anterior part of the iliac crest.

• Distal Attachment: Iliotibial tract into the lateral condyle of the tibia (Gerdy's Tubercle).

• Action: Flexion, abduction, and internal rotation of the thigh. Works with the gluteus maximus to stabilize the hip joint and stabilize the extended knee.

• Innervation: Superior gluteal nerve ($L4$-$S1$).

• Artery: Superior gluteal artery.

Deep Lateral Rotators of the Hip

Piriformis

• Proximal Attachment: Anterior surface of the sacrum; greater sciatic notch; sacrotuberous ligament.

• Distal Attachment: Greater trochanter of the femur.

• Action: External rotation (ER) of the extended hip; abducts the thigh when the hip is flexed; stabilizes the hip joint.

• Innervation: Spinal nerves $S1$, $S2$.

• Artery: Superior gluteal artery, inferior gluteal artery, and internal pudendal artery.

Superior Gemellus

• Proximal Attachment: Ischial spine.

• Distal Attachment: Greater trochanter of the femur (via the tendon of the obturator internus).

• Action: External rotation of the hip; abducts flexed thigh; stabilizes hip joint.

• Innervation: Nerve to obturator internus ($L5$, $S1$).

• Artery: Inferior gluteal artery.

Obturator Internus

• Proximal Attachment: Pelvic surface of the ilium and ischium; obturator membrane.

• Distal Attachment: Greater trochanter of femur.

• Action: External rotation of hip; abducts flexed thigh; stabilizes hip joint.

• Innervation: Nerve to obturator internus ($L5$, $S1$).

• Artery: Internal pudendal artery.

Inferior Gemellus

• Proximal Attachment: Ischial tuberosity.

• Distal Attachment: Greater trochanter of the femur (via the tendon of the obturator internus).

• Action: External rotation of the hip; abducts flexed thigh; stabilizes hip joint.

• Innervation: Nerve to quadratus femoris ($L5$, $S1$).

• Artery: Inferior gluteal artery.

Obturator Externus

• Proximal Attachment: External surface of the obturator foramen and obturator membrane.

• Distal Attachment: Trochanteric fossa of the femur.

• Action: External rotation (ER) of the hip; stabilizes hip joint.

• Innervation: Obturator nerve ($L3$-$L4$).

• Artery: Medial circumflex femoral artery and obturator artery.

Quadratus Femoris

• Proximal Attachment: Ischial tuberosity.

• Distal Attachment: Quadrate tubercle on the intertrochanteric crest of the femur.

• Action: External rotation of thigh; stabilizes hip joint.

• Innervation: Nerve to quadratus femoris ($L5$-$S1$).

• Artery: Medial circumflex femoral artery.

Anterior Thigh Compartment

Iliopsoas (Psoas Major & Iliacus)

• Proximal Attachment: Sides of $T12$-$L5$ vertebrae and the discs between them; transverse processes of all lumbar vertebrae.

• Distal Attachment: Lesser trochanter of the femur.

• Action: Flexes hip; flexes trunk; stabilizes hip; serves as a postural muscle to help control deviation of the trunk.

• Innervation: Anterior rami of $L1$-$L3$.

• Artery: Internal iliac artery.

Sartorius

• Proximal Attachment: Anterior superior iliac spine (ASIS).

• Distal Attachment: Pes anserine.

• Action: Flexes, abducts, and externally rotates the thigh; flexes the knee.

• Innervation: Femoral nerve ($L2$-$L3$).

• Artery: Femoral artery.

Pectineus

• Proximal Attachment: Superior ramus of the pubis.

• Distal Attachment: Pectineal line of the femur just inferior to the lesser trochanter.

• Action: Adducts and flexes thigh/hip.

• Innervation: Femoral nerve ($L2$-$L3$); sometimes receives innervation from the obturator nerve.

• Artery: Medial circumflex artery, femoral artery, and obturator artery.

Vastus Lateralis

• Proximal Attachment: Greater trochanter of the femur; lateral lip of the linea aspera.

• Distal Attachment: Tibial tuberosity via the patellar ligament.

• Action: Extends leg at the knee joint.

• Innervation: Femoral nerve ($L2$-$L4$).

• Artery: Femoral artery.

Vastus Medialis

• Proximal Attachment: Intertrochanteric line; medial lip of the linea aspera.

• Distal Attachment: Tibial tuberosity via the patellar ligament.

• Action: Extends leg at the knee joint.

• Innervation: Femoral nerve ($L2$-$L4$).

• Artery: Femoral artery.

Vastus Intermedius

• Proximal Attachment: Anterior and lateral surfaces of the body of the femur.

• Distal Attachment: Tibial tuberosity via the patellar ligament.

• Action: Extends leg at the knee joint.

• Innervation: Femoral nerve ($L2$-$L4$).

• Artery: Femoral artery.

Rectus Femoris

• Proximal Attachment: Anterior inferior iliac spine (AIIS); ilium superior to the acetabulum.

• Distal Attachment: Tibial tuberosity via the patellar ligament.

• Action: Extends leg at the knee; flexes thigh at the hip.

• Innervation: Femoral nerve ($L2$-$L4$).

• Artery: Femoral artery.

Medial Thigh Compartment

Gracilis

• Proximal Attachment: Body of the pubis and inferior ramus of the pubis.

• Distal Attachment: Pes anserine.

• Action: Adducts thigh; flexes leg; when the knee is flexed, it performs internal rotation (IR) of the leg.

• Innervation: Obturator nerve ($L2$-$L3$).

• Artery: Deep femoral artery.

Adductor Longus

• Proximal Attachment: Body of the pubis inferior to the pubic crest.

• Distal Attachment: Middle third of the linea aspera of the femur.

• Action: Adducts thigh; flexes and medially rotates the thigh.

• Innervation: Obturator nerve ($L2$-$L4$).

• Artery: Deep femoral artery.

Adductor Brevis

• Proximal Attachment: Body and inferior ramus of the pubis.

• Distal Attachment: Pectineal line and proximal part of the linea aspera of the femur.

• Action: Adducts thigh; acts as a weak hip flexor and medial rotator.

• Innervation: Obturator nerve ($L2$-$L4$).

• Artery: Deep femoral artery.

Adductor Magnus

• Proximal Attachment:

  • Adductor part: Inferior pubic ramus and ramus of the ischium.

  • Hamstring part: Ischial tuberosity.

• Distal Attachment:

  • Adductor part: Gluteal tuberosity, linea aspera, and medial supracondylar line.

  • Hamstring part: Adductor tubercle of the femur.

• Action: Adducts and flexes the thigh; the hamstring part extends the thigh.

• Innervation:

  • Adductor part: Obturator nerve ($L2$-$L4$).

  • Hamstring part: Tibial division of the sciatic nerve ($L4$).

• Artery: Deep femoral artery.

Anterior Leg Compartment

Extensor Digitorum Longus

• Proximal Attachment: Lateral condyle of the tibia; superior medial fibula; interosseous membrane.

• Distal Attachment: Middle and distal phalanges of toes $2$-$5$.

• Action: Extends the lateral four digits (toes $2$-$5$); dorsiflexes the foot.

• Innervation: Deep fibular nerve ($L5$-$S1$).

• Artery: Anterior tibial artery.

Extensor Hallucis Longus

• Proximal Attachment: Middle part of the anterior fibula and the interosseous membrane.

• Distal Attachment: Dorsal base of the distal phalanx of the great toe.

• Action: Extends the great toe; dorsiflexes the foot; acts as a weak invertor.

• Innervation: Deep fibular nerve ($L5$-$S1$).

• Artery: Anterior tibial artery.

Tibialis Anterior

• Proximal Attachment: Lateral condyle of the tibia; superior lateral tibia; interosseous membrane.

• Distal Attachment: Medial and inferior surface of the medial cuneiform; base of the $1st$ metatarsal.

• Action: Dorsiflexes the ankle; inverts the foot; supports the medial longitudinal arch.

• Innervation: Deep fibular nerve ($L4$-$L5$).

• Artery: Anterior tibial artery.

Fibularis Tertius

• Proximal Attachment: Inferior part of the anterior fibula; interosseous membrane.

• Distal Attachment: Dorsal base of the $5th$ metatarsal.

• Action: Dorsiflexes the foot; everts the foot.

• Innervation: Deep fibular nerve ($L5$-$S1$).

• Artery: Anterior tibial artery.

Lateral Leg Compartment

Fibularis Brevis

• Proximal Attachment: Distal $\frac{2}{3}$ of the lateral fibula.

• Distal Attachment: Lateral side of the base of the $5th$ metatarsal.

• Action: Everts the foot; weakly plantarflexes the foot; supports the transverse arch of the foot.

• Innervation: Superficial fibular nerve ($L5$-$S2$).

• Artery: Fibular artery.

Fibularis Longus

• Proximal Attachment: Fibular head; superior lateral surface of the fibula.

• Distal Attachment: Base of the $1st$ metatarsal; medial cuneiform.

• Action: Everts the foot; weakly plantarflexes the foot; supports the transverse arch of the foot.

• Innervation: Superficial fibular nerve ($L5$-$S2$).

• Artery: Fibular artery.

Posterior Leg Compartment

Gastrocnemius

• Proximal Attachment:

  • Lateral head: Lateral condyle of the femur.

  • Medial head: Popliteal surface of the femur, superior to the medial condyle.

• Distal Attachment: Posterior aspect of the calcaneus via the calcaneal tendon.

• Action: Plantarflexes the foot; flexes the knee; raises the heel during walking.

• Innervation: Tibial nerve ($S1$-$S2$).

• Artery: Posterior tibial artery.

Soleus

• Proximal Attachment: Posterior fibular head; superior part of the posterior fibula; soleal line and medial border of the tibia.

• Distal Attachment: Posterior aspect of the calcaneus via the calcaneal tendon.

• Action: Plantarflexes the foot; stabilizes the leg over the foot (critical for posture).

• Innervation: Tibial nerve ($S1$-$S2$).

• Artery: Posterior tibial artery.

Plantaris

• Proximal Attachment: Inferior end of the lateral supracondylar line of the femur; oblique popliteal ligament.

• Distal Attachment: Posterior aspect of the calcaneus via the calcaneal tendon.

• Action: Weakly assists the gastrocnemius in plantarflexion and knee flexion.

• Innervation: Tibial nerve ($S1$-$S2$).

• Artery: Posterior tibial artery.

Popliteus

• Proximal Attachment: Lateral surface of the lateral condyle of the femur and the lateral meniscus.

• Distal Attachment: Posterior surface of the tibia, superior to the soleal line.

• Action: Flexes and medially rotates the leg at the knee. When the limb is weight-bearing, it rotates the femur laterally on the tibia to "unlock" the knee joint.

• Innervation: Tibial nerve ($L4$-$S1$).

• Artery: Posterior tibial artery.

Tibialis Posterior

• Proximal Attachment: Posterior tibia inferior to the soleal line; posterior fibula; interosseous membrane.

• Distal Attachment: Tuberosity of the navicular bone; plantar surfaces of the cuboid and cuneiform bones; bases of the $2nd$-$4th$ metatarsals.

• Action: Plantarflexes the foot; inverts the foot; maintains the medial longitudinal arch of the foot.

• Innervation: Tibial nerve ($L4$-$L5$).

• Artery: Posterior tibial artery.

Flexor Hallucis Longus

• Proximal Attachment: Inferior $\frac{2}{3}$ of the posterior surface of the fibula; inferior part of the interosseous membrane.

• Distal Attachment: Base of the distal phalanx of the great toe.

• Action: Flexes the distal phalanx of the big toe; plantarflexes the ankle; helps propel the foot during walking or running; supports the medial longitudinal arch.

• Innervation: Tibial nerve ($S2$, $S3$).

• Artery: Posterior tibial artery.

Flexor Digitorum Longus

• Proximal Attachment: Medial part of the posterior tibia inferior to the soleal line; broad tendon to the fibula.

• Distal Attachment: Base of the distal phalanges of the $2nd$-$5th$ toes.

• Action: Flexes the lateral four digits; plantarflexes the foot; supports the longitudinal arches; aids with inversion.

• Innervation: Tibial nerve ($S2$, $S3$).

• Artery: Posterior tibial artery.

Foot: Dorsal Surface

Extensor Digitorum Brevis

• Proximal Attachment: Calcaneus.

• Distal Attachment: Long extensor tendons of toes.

• Action: Aids the Extensor Digitorum Longus (EDL) in extending the toes.

• Innervation: Deep fibular nerve ($L5$, $S1$).

• Artery: Dorsalis pedis artery.

Extensor Hallucis Brevis

• Proximal Attachment: Dorsum of the calcaneus.

• Distal Attachment: Dorsal base of the proximal phalanx of the big toe.

• Action: Extends the proximal phalanx of the big toe; aids the Extensor Hallucis Longus (EHL).

• Innervation: Deep fibular nerve ($L5$, $S1$).

• Artery: Dorsalis pedis artery.

Foot: Plantar Surface (1st Layer)

Abductor Digiti Minimi

• Proximal Attachment: Medial and lateral tubercles of the tuberosity of the calcaneus; plantar aponeurosis; intermuscular septum.

• Distal Attachment: Lateral side of the base of the proximal phalanx of the $5th$ digit.

• Action: Abducts and flexes the $5th$ digit.

• Innervation: Lateral plantar nerve ($S1$-$S3$).

• Artery: Lateral plantar artery.

Abductor Hallucis

• Proximal Attachment: Medial tubercle of the calcaneal tuberosity; flexor retinaculum; plantar aponeurosis.

• Distal Attachment: Medial aspect of the base of the proximal phalanx of the big toe.

• Action: Abducts and flexes the $1st$ digit at the metatarsophalangeal (MTP) and interphalangeal (IP) joints.

• Innervation: Medial plantar nerve ($S1$-$S3$).

• Artery: Medial plantar artery.

Flexor Digitorum Brevis

• Proximal Attachment: Medial tubercle of the tuberosity of the calcaneus; plantar aponeurosis; intermuscular septum.

• Distal Attachment: Both sides of the middle phalanges of digits $2$-$5$.

• Action: Flexes the lateral four digits at the MTP and IP joints.

• Innervation: Medial plantar nerve ($S1$-$S3$).

• Artery: Medial plantar artery.

Foot: Plantar Surface (2nd Layer)

Quadratus Plantae

• Proximal Attachment: Medial surface and lateral margin of the plantar surface of the calcaneus.

• Distal Attachment: Posterolateral margin of the Flexor Digitorum Longus (FDL) tendon.

• Action: Assists the FDL in flexing digits $2$-$5$.

• Innervation: Lateral plantar nerve ($S1$-$S3$).

• Artery: Medial and lateral plantar arteries.

Lumbrical Muscles

• Proximal Attachment: Tendons of the flexor digitorum longus.

• Distal Attachment: Medial aspect of the expansion over the lateral 4 digits (extensor sheath).

• Action: Flex the proximal phalanges at the MTP joints and extend the two distal phalanges of the four lateral digits.

• Innervation:

  • Medial $1$: Medial plantar nerve ($S1$-$S3$).

  • Lateral $3$: Lateral plantar nerve ($S1$-$S3$).

• Artery: Medial and lateral plantar arteries.

Foot: Plantar Surface (3rd Layer)

Flexor Hallucis Brevis

• Proximal Attachment: Plantar surfaces of the cuboid and lateral cuneiform.

• Distal Attachment: Both sides of the base of the proximal phalanx of the $1st$ digit.

• Action: Flexes the proximal phalanx of the $1st$ digit (flexes the proximal IP joint of the $1st$ digit).

• Innervation: Medial plantar nerve ($S1$-$S3$).

• Artery: Medial and lateral plantar arteries.

Adductor Hallucis

• Proximal Attachment:

  • Oblique head: Bases of metatarsals $2$-$4$.

  • Transverse head: Plantar ligaments of the $3rd$-$5th$ MTP joints.

• Distal Attachment: Tendons of both heads attach to the lateral side of the base of the proximal phalanx of the $1st$ digit.

• Action: Adducts the $1st$ digit and flexes the proximal phalanx at the MTP joint; assists in maintaining the transverse arch of the foot.

• Innervation: Lateral plantar nerve ($S1$-$S3$).

• Artery: Medial and lateral plantar arteries.

Flexor Digiti Minimi Brevis

• Proximal Attachment: Base of the $5th$ metatarsal.

• Distal Attachment: Base of the proximal phalanx of the $5th$ digit.

• Action: Flexes the proximal phalanx of the $5th$ digit.

• Innervation: Lateral plantar nerve ($S1$-$S3$).

• Artery: Medial and lateral plantar arteries.

Foot: Plantar Surface (4th Layer)

Plantar Interossei ($3$ muscles)

• Proximal Attachment: Bases (plantar aspect) and medial sides of metatarsals $3$-$5$.

• Distal Attachment: Medial sides of the bases of the proximal phalanges of digits $3$-$5$.

• Action: Adduct digits $3$-$5$, flex MTP joints, and extend the distal phalanges.

• Innervation: Lateral plantar nerve ($S1$-$S3$).

• Artery: Medial and lateral plantar arteries.

Dorsal Interossei ($4$ muscles)

• Proximal Attachment: Adjacent sides of metatarsals $1$-$5$.

• Distal Attachment:

  • $1st$: Medial side of the proximal phalanx of digit $2$.

  • $2nd$-$4th$: Lateral sides of digits $2$-$4$.

• Action: Abduct digits $2$-$4$, flex MTP joints, and extend the distal phalanges.

• Innervation: Lateral plantar nerve ($S1$-$S3$).

• Artery: Medial and lateral plantar arteries.