Lower Extremity Muscles

Psoas major

O: transverse processes of lumbar vertebrae (bodies, intervertebral disks)

In: lesser trochanter of femur

A: flexes thigh + trunk

I: L2 and L3 branches of lumbar plexus

Iliacus

O: upper 2/3 of iliac fossa

In: lesser trochanter with tendon of psoas major

A: flexes thigh

I: femoral nerve

Gluteus Maximus

O: outer surface of ilium, adjacent posterior surface of sacrum + coccyx

In: iliotibial tract; gluteal tuberosity

A: abducts, extends, and laterally rotates thigh

I: inferior gluteal nerve

Gluteus Medius

O: outer surface of ilium inferior to iliac crest

In: lateral surface of greater trochanter

A: abducts and medially rotates thigh

I: superior gluteal nerve

Gluteus minimus

O: outer surface of ilium between anterior and inferior gluteal line

In: anterior surface of greater trochanter

A: abducts and medially rotates thigh

I: superior gluteal nerve

Tensor Fascia Latae

O: outer lip of iliac crest between ASIS and iliac tubercle

In: upper part of iliotibial tract

A: abducts + flexes thigh

I: superior gluteal nerve

Piriformis

O: internal surface of sacrum

In: upper border of greater trochanter

A: laterally rotates + abducts thigh

I: 1st and 2nd sacral nerve

Obturator Internus

O: internal pelvic surface of obturator membrane

In: common tendon w/ superior + inferior gemelli to medial surface of greater trochanter

A: laterally rotates thigh + stabilize femoral head

I: nerve to obturator internus

Gemellus Superior

O: spine of ischium

In: with the tendon of obturator internus into upper border of greater trochanter

A: laterally rotates thigh + stabilizes hip

I: branch of nerve to obturator internus from sacral plexus

Gemellus Inferior

O: upper margin of ischial tuberosity

In: w/ tendon of obturator internus into upper border of greater trochanter

A: laterally rotates thigh + stabilize femoral head

I: branch of nerve to quadratus femoris from sacral plexus

Quadratus Femoris

O: lateral border of ischial tuberosity

In: below intertrochanteric crest

A: laterally rotates thigh

I: nerve to quadratus femoris

Obturator Externus

O: outer surface of inferior + superior rami of pubis, ramus of ischium

In: trochanteric fossa of femur

A: lateral thigh

I: obturator nerve

Sartorius

(crosses hip to knee)

(longest muscle in body, called “tailor’s muscle”)

O: ASIS (anterior superior iliac spine)

In: upper part of medial surface of shaft of tibia

A: flexes, abducts, external rotation of femur; slight internal rotation of leg at knee joint after flexion

I: femoral nerve

Rectus Femoris

(crosses hip and knee)

O: AIIS (anterior interior iliac spine)

In: tibial tuberosity via patellar tendon

A: flexes thigh, extends leg

I: femoral nerve

Vastus Lateralis

O: Intertrochanteric line

In: tibial tuberosity via patellar tendon

A: extends leg

I: femoral nerve

Vastus Medialis

O: intertrochanteric line

In: tibial tuberosity via patellar tendon

A: extends leg

I: femoral nerve

Vastus Intermedius

O: anterior and lateral 2/3 of femur

In: tibial tuberosity via patellar tendon

A: extends leg

I: femoral nerve

Gracilis

O: pubic ramus

In: upper, medial shaft of tibia

A: adducts thigh, also flexes knee + medially rotates leg when knee is flexed

I: obturator nerve

Pectineus

O: superior ramus of pubis

In: lesser trochanter

A: flexes thigh, assists in adduction when hip flexed

I: femoral nerve (some people receive contribution from obturator nerve)

Adductor Longus

O: anterior pubis

In: linea aspera

A: adducts thigh, assists w/ hip flexion + medial rotation

I: obturator nerve

Adductor Brevis

(deep to adductor longus)

O: inferior ramus of pubis

In: linea aspera

A: adducts thigh

I: obturator nerve

Adductor Magnus

O: inferior ramus of pubis

In: linea aspera, adductor tubercle of femur

A: adducts + extends thigh

I: obturator nerve

Biceps Femoris

O: Long Head: ischial tuberosity - Short Head: linea aspera

In: head of fibula

A: flexes knee; Long head: extends thigh

I: Long Head: tibial nerve; Short: common peroneal nerve

Semitendinosus

O: ischial tuberosity

In: medial, superior tibia

A: flexes knee, extends thigh

I: tibial nerve

Semimembranosus

O: ischial tuberosity

In: posterior, superior thigh

A: flexes knee, extends thigh

I: tibial nerve

anterior thigh muscles

extends knee

medial thigh muscles

adducts thigh

posterior thigh muscles

flexes knee, extends hip

Lower Leg - Anterior Compartment

• all assist dorsiflexion

• innervated by deep peroneal/fibular nerve

Tibialis Anterior (anterior compartment)

tendon passes over ankle

O: lateral condyle of tibia, upper ½ of lateral surface of tibia, interosseous membrane

In: medial and plantar surface of medial cuneiform, base of 1st metatarsal

A: dorsiflexion, inversion of the foot

I: deep peroneal

Extensor Hallucis Longus (anterior compartment)

thinner + lies deeper than tibialis anterior

crosses to great toe

O: middle half of anterior fibula, interosseous membrane

In: base of distal phalanx of great toe

A: extends + hyperextends great toe, dorsiflexion + inverts foot

I: deep peroneal

Extensor Digitorum Longus (anterior compartment)

O: upper 2/3 of anterior fibula, interosseous membrane, lateral condyle of TIBIA

In: dorsal surface of lateral 4 toes, base of middle and distal phalanges

A: extends toes 2-5, dorsiflexion an eversion of foot

I: deep peroneal

Peroneus (fibularis) tertius [anterior compartment]

O: lower 1/3 of fibula; interosseous membrane

In: dorsal surface of the base of the 5th metatarsal

A: dorsiflexion and eversion of foot

I: deep peroneal

Lower Leg - Superficial Posterior Compartment

• all contribute to plantarflexion

• innervated by tibial nerve

Gastrocnemius (superficial posterior compartment)

O: Lateral Head: lateral condyle and posterior surface of femur; Medial Head: popliteal surface of femur above medial condyle

In: posterior surface of calcaneus through the Achilles tendon

A: plantarflexion of foot, flexes leg at knee

I: tibial nerve

Soleus (superficial posterior compartment)

lies deep to gastrocnemius

does NOT cross knee\

primary for plantarflexion when knee is flexed (seated)

O: posterior surface of tibia, upper 2/3 of posterior surface of the fibula, fibrous arch between tibia + fibula

In: posterior surface of calcaneus via the Achilles tendon

A: plantarflexion of foot

I: tibial nerve

Plantaris (superficial posterior compartment)

O: lateral supracondylar ridge of femur, oblique popliteal ligament

In: posterior surface of calcaneus

A: plantarflexion of foot; flexes leg at knee (weakly assists both)

I: tibial nerve

Lower Leg - (deep posterior compartment)

• all receive the tibial nerve

Popliteus (deep posterior compartment)

O: lateral surface of the lateral condyle of the femur

In: upper part of the posterior surface of the tibia

A: “unlocks,” medial rotation of leg, flexion of the leg, also helps stabilize knee

I: tibial nerve

Flexor Hallucis Longus (deep posterior compartment)

O: lower 2/3 of posterior surface of the shaft of the fibula, posterior intermuscular septum, interosseous membrane

In: base of distal phalanx of the great toe

A: flexion of great toe (distal phalanx), assist PF and inversion of foot

I: tibial nerve

Flexor Digitorum Longus (deep posterior compartment)

O: medial part of the posterior surface of the tibia

In: base of 2-5 distal phalanges

A: flexion of 2-5 distal phalanges, assist PF and inversion of foot

I: tibial nerve

Tibialis Posterior (deep posterior compartment)

O: lateral part of the posterior surface of the tibia, proximal ½ of the posterior surface of the fibula, interosseous membrane

In: navicular tuberosity, cuboid, cuneiforms, 2-4 metatarsals, sustentaculum tali

A: plantarflexion + inversion of foot; supports the medial longitudinal arch

I: tibial nerve

Lower Leg - Lateral Compartment

• plantarflexion + eversion

• superficial peroneal nerve

Peroneus (fibularis) longus [lateral compartment]

O: upper 2/3 of lateral surface of the fibula

In: lateral surface medial cuneiform, base of 1st metatarsal

A: plantarflexion + eversion of foot

I: superficial peroneal nerve

Peroneus (fibularis) Brevis [lateral compartment]

stays lateral

O: lower 2/3 of lateral surface of the fibula

In: lateral side of the base of the 5th metatarsal

A: plantarflexion + eversion of foot

I: superficial peroneal nerve

Extensor Digitorum Brevis

O: anterior + lateral surface of calcaneus; lateral talocalcaneal ligament, inferior extensor retinaculum

In: extensor digitorum longus tendons + extensor expansions of toes 2-4 (some muscles attach to other muscle’s tendons

A: extension of 2-4 toes

I: deep peroneal nerve

Abductor Hallucis

O: tuberosity of the calcaneus, flexor retinaculum and plantar aponeurosis

In: medial side of base of 1st proximal phalanx

A: abducts and stabilizes the great toe, flexion at MT joint

I: medial plantar nerve

Flexor Digitorum Brevis

O: tuberosity of the calcaneus; plantar aponeurosis

In: sides of middle phalanges of toes 2-5

A: flexes proximal interphalangeal (PIP) joints of toes 2-5; assists metatarsophalangeal (MTP) joint flexion

I: medial plantar nerve

Abductor Digiti Minimi

O: tuberosity of the calcaneus; plantar aponeurosis

In: lateral side of 5th proximal phalanx

A: abducts 5th toe, assists flexion a MTP joint

I: lateral plantar nerve

Lumbricales

O: tendons of flexor digitorum longus

In: medial sides of extensor expansions of toes 2-5

A: flexes MTP joints and extends PIP joints of toes 2-5 (think of hand lumbricales; bend at knuckle, keep fingers straight)

I: 1st lumbrical (most medial) - medial plantar nerve; 2-4 (lateral 3) - lateral plantar nerve

Flexor Hallucis Brevis

O: cuboid, lateral cuneiform

In: medial + lateral sides of the base of 1st proximal phalanx

A: flex proximal phalanx of great toe (MTP joint)

I: medial plantar nerve

Adductor Hallucis

O: Oblique head: 2-4 metatarsal bones, sheath of peroneus longus tendon; Transverse head: plantar metatarsophalangeal ligaments of 3, 4, 5. transverse metatarsal ligament

In: lateral side of base of 1st proximal phalanx

A: adducts and stabilizes the great toe

I: lateral plantar nerve

Flexor Digiti Minimi Brevis

O: Base of 5th metatarsal; sheath of peroneus longus tendon

In: lateral sides of the base of the 5th proximal phalanx

A: flex proximal phalanx of 5th toe

I: lateral plantar nerve

Dorsal Interossei

DAB - dorsal

ABduct

O: adjacent sides of metatarsal bones

In: 1st - medial side of proximal phalanx of 2nd toe; 2-4: lateral sides of proximal phalanges of 2-4 toes

A: abduct toes, flex proximal phalanges

I: lateral plantar nerve

Plantar Interossei

PAD - plantar ADduct

O: medial aspect of metatarsals 3-5

In: proximal phalanges 3-5

A: adduct toes, flex proximal phalanges

I: lateral planter nerve