Flexor hallucis longus

Flexor hallucis longus muscle
The mucous sheaths of the tendons around the ankle. Medial aspect. (Flexor hallucis longus visible at bottom center.)
Details
Origin	fibula, posterior aspect of middle 1/3
Insertion	Plantar surface; base of distal phalanx of hallux
Artery	Peroneal artery (peroneal branch of the posterior tibial artery)
Nerve	tibial nerve, S1 & S2 more than L5 nerve roots
Actions	flexes all joints of the big toe, plantar flexion of the ankle joint
Antagonist	Extensor hallucis longus muscle
Identifiers
Latin	Musculus flexor hallucis longus
TA	A04.7.02.053
FMA	22593
Anatomical terms of muscle []

The Flexor hallucis longus muscle (FHL) is one of the three deep muscles of the posterior compartment of the leg that distally attaches to the plantar surface of the distal phalanx of the hallux (great or big toe). The other deep muscles are the flexor digitorum longus and tibialis posterior; the tibialis posterior is the most powerful of these deep muscles. All three muscles are innervated by the tibial nerve which comprises half of the sciatic nerve.

The Flexor hallucis longus is situated on the fibular side of the leg. It arises from the inferior two-thirds of the posterior surface of the body of the fibula, with the exception of 2.5 cm. at its lowest part; from the lower part of the interosseous membrane; from an intermuscular septum between it and the Peronæi, laterally, and from the fascia covering the Tibialis posterior, medially.

The fibers pass obliquely downward and backward, where it passes through the tarsal tunnel on the medial side of the foot and end in a tendon which occupies nearly the whole length of the posterior surface of the muscle.

This tendon lies in a groove which crosses the posterior surface of the lower end of the tibia, between the medial and lateral tubercoles of the posterior surface of the talus, and the under surface of the sustentaculum tali of the calcaneus; in the sole of the foot it runs forward between the two heads of the Flexor hallucis brevis, and is inserted into the base of the last phalanx of the great toe. The grooves on the talus and calcaneus, which contain the tendon of the muscle, are converted by tendinous fibers into distinct canals, lined by a mucous sheath.

As the tendon passes forward in the sole of the foot, it is situated above, and crosses from the lateral to the medial side of the tendon of the Flexor digitorum longus, to which it is connected by a fibrous slip.