Name

# Flexor Hallicus Longus

Pronunciation

(FLEK-sur HA-loo-sus LONG-gus)

Origin/Proximal Attachment

Distal two 3rd’s of posterior surface of fibula (except for lowest 2.5 cm or so)

Interosseous membrane

Crural fascia (which covers tibialis posterior)

Posterior crural intermuscular septum

Insertion/Distal Attachment

Plantar surface of base of distal phalanx of hallux (big toe)

Action/Relevance

Flexes big toe

Weakly plantar-flexes foot

Weakly adducts & inverts foot

Innervation

Tibial nerve (L5, S1, 2)

Notes

Its fibres run obliquely down to a tendon that occupies nearly the whole length of the posterior aspect of the muscle

the tendon grooves the posterior surface of the lower end of the tibia, posterior surface of the talus, followed by the inferior surface of the sustentaculum tali of the calcaneus

the grooves on the talus & calcaneus are converted by fibrous bands into a canal, lined by a synovial sheath

in the sole ofr the foot it crosses the flexor digitorum longus from the lateral to the medial side, curving obliquely superior to it (at the crossing point the long digital flexor receives a fibrous slip from the flexor hallucis longus tendon)

the tendon then crosses the lateral part of flexor hallucis brevis to reach the interval between the sesamoid bones under the head of the first metatarsal

It continues along the plantar aspect of the hallux, running in an osseo-aponeurotic tunnel to the attachment point