Muscles 77-101 (Lower Leg + Foot)

Tibialis Anterior

Origin: Lateral condyle of tibia; lateral surface of tibia ; Interosseous membrane.

Insertion: Medial cuneiform; Base of the 1st metatarsal.

Action: DF ankle joint; IV subtalar joint; supports medial longitudinal arch of foot.

Innervation: Deep fibular nerve (L4, L5).

Extensor Hallucis Longus

Origin: Mid + anterior surface of fibula; Interosseous membrane.

Insertion: Distal phalanx of 1st toe.

Action: EXT great toe; DF ankle joint.

Innervation: Deep fibular nerve (L5, S1).

Extensor Digitorum Longus

Origin: Lateral condyle of tibia; Prox + Anterior shaft of fibula; Interosseous membrane.

Insertion: Middle and distal phalanges of toes 2-5.

Action: EXT digits 2-5; DF ankle joint.

Innervation: Deep fibular nerve (L5, S1).

Fibularis Tertius

Origin: Inferior anterior surface of fibula; Interosseous membrane.

Insertion: Dorsum of base of 5th metatarsal.

Action: DF ankle joint; assist EV of subtalar joint.

Innervation: Deep fibular nerve (L5, S1).

Fibularis Longus

Origin: Head of fibula; Prox + lateral fibula.

Insertion: Base of the 1st metatarsal; Medial cuneiform.

Action: EV subtalar joint; weakly PF ankle joint; Supports transverse arch of foot.

Innervation: Superficial fibular nerve (L5, S1, S2).

Fibularis Brevis

Origin: Mid + lateral fibula.

Insertion: Tuberosity of fifth metatarsal.

Action: EV subtalar joint; weakly PF ankle joint.

Innervation: Superficial fibular nerve (L5, S1, S2).

Gastrocnemius

Origin: Post surface of condyles of the femur.

Insertion: Calcaneus via calcaneal (Achilles) tendon.

Action: Flex knee; PF ankle joint.

Innervation: Tibial nerve (S1, S2).

Soleus

Origin: Soleal line; Prox + Post surface of tibia; Post aspect of head of fibula.

Insertion: Calcaneus via calcaneal (Achilles) tendon.

Action: PF the ankle.

Innervation: Tibial nerve (S1, S2).

Plantaris

Origin: Lateral supracondylar line of femur.

Insertion: Calcaneus via calcaneal (Achilles) tendon.

Action: Weakly assists the gastrocnemius; function is likely proprioceptive.

Innervation: Tibial nerve (S1, S2).

Popliteus

Origin: Lat condyle of the femur; Lat meniscus.

Insertion: Prox + Post aspect of tibia.

Action: Weakly Flex knee joint; unlocks it by ER femur on fixed tibia or IR tibia of unplanted limb.

Innervation: Tibial nerve (L4, L5, S1).

Flexor Hallucis Longus

Origin: Mid half of posterior fibula.

Insertion: Distal phalanx of digit 1.

Action: Flex 1st toe; Weak PF ankle; IV foot.

Innervation: Tibial nerve (S2, S3).

Flexor Digitorum Longus

Origin: Mid + Post surface of tibia.

Insertion: Distal phalanges of digits 2-5.

Action: Flex digits 2-5; Weak PF of ankle; IV foot.

Innervation: Tibial nerve (S2, S3).

Tibialis Posterior

Origin: Prox + Post shafts of tibia and fibula; Interosseous membrane.

Insertion: All 5 tarsal bones; Bases of 2nd-4th metatarsals.

Action: PF ankle joint; IV foot; maintains medial longitudinal arch of foot.

Innervation: Tibial nerve (L4, L5).

Abductor Hallucis

Origin: Medial process of calcaneus; Plantar aponeurosis.

Insertion: Medial side of base of Prox phalanx of 1st digit.

Action: ABD 1st toe; assists to flex 1st toe.

Innervation: Tibial nerve (L5, S1).

Flexor Digitorum Brevis

Origin: Medial process of calcaneus; Plantar aponeurosis.

Insertion: Middle phalanges of digits 2-5.

Action: Flex MTP and PIP joints of digits 2-5.

Innervation: Tibial nerve (L5, S1).

Abductor Digiti Minimi

Origin: Lat process of calcaneus; Plantar aponeurosis.

Insertion: Prox phalanx of digit 5.

Action: ABD and Flex digit 5.

Innervation: Tibial nerve (S1, S2, S3).

Quadratus Plantae

Origin: Medial + Lat sides of plantar surface of calcaneus.

Insertion: Post + Lat aspect of flexor digitorum longus tendon.

Action: Assist flexor digitorum longus to flex digits 2-5.

Innervation: Tibial nerve (S1, S2, S3).

Lumbricals

Origin: Tendons of flexor digitorum longus.

Insertion: Medial aspect of extensor expansion over digits 2-5.

Action: Flexes MTP joint; EXT PIP/DIP joints of digits 2-5.

Innervation: Tibial nerve (L5 – S3).

Flexor Hallucis Brevis

Origin: Plantar surfaces of Cuboid + Lat cuneiform.

Insertion: Both sides of base of proximal phalanx of 1st digit.

Action: Flex MTP joint of the great toe.

Innervation: Tibial nerve (L5, S1).

Adductor Hallucis

Origin: Oblique head - Bases of 2nd-4th metatarsals. Transverse head - Plantar ligament of 3rd-5th MTP joints.

Insertion: Lat surface of base of Prox phalanx of 1st toe.

Action: ADD 1st digit; assists in maintaining transverse arch of foot.

Innervation: Tibial nerve (S1 – S3).

Flexor Digiti Minimi Brevis

Origin: Base of 5th metatarsal.

Insertion: Base of Prox phalanx of 5th toe.

Action: Flex PIP joint of the 5th digit.

Innervation: Tibial nerve (S1 – S3).

Plantar Interossei (3 muscles)

Origin: Medial surfaces of 3rd-5th metatarsals.

Insertion: Medial surfaces of Prox phalanges of 3rd-5th toes.

Action: ADD and Flex 3rd-5th MTP joints.

Innervation: Tibial nerve (S1 – S3).

Dorsal Interossei (4 muscles)

Origin: Adjacent surfaces of metatarsals 1-5.

Insertion: 1st - Medial surface of Prox phalanx of 2nd toe. 2nd-4th - Lat surfaces of Prox phalanges of 2nd-4th toes.

Action: ABD and Flex 2nd-4th MTP joints.

Innervation: Tibial nerve (S1 – S3).

Extensor Hallucis Brevis

Origin: Dorsal surface of calcaneus.

Insertion: Prox phalanx of 1st toe.

Action: EXT 1st toe.

Innervation: Deep fibular nerve (L4 - S1).

Extensor Digitorum Brevis

Origin: Dorsal surface of calcaneus.

Insertion: 2nd-4th toes via the extensor digitorum longus tendons.

Action: EXT 2nd-4th toes.

Innervation: Deep fibular nerve (L4 - S1).