Flexor hallucis longus
Musculus flexor hallucis longus
Also known as: FHL, dancer's tendon
A powerful deep muscle from the posterior fibula to the distal phalanx of the great toe. It provides the final push-off in gait and supports the medial arch.
Overview
FHL arises from the lower two-thirds of the posterior surface of the fibula and the interosseous membrane. Despite its lateral origin, its tendon grooves the back of the distal tibia and the posterior process of the talus (between its tubercles). It then runs under the sustentaculum tali, which acts as a pulley, crosses deep to FDL in the sole and inserts on the base of the distal phalanx of the great toe. It is the most posterior structure behind the medial malleolus.
It flexes all the joints of the hallux. It is the muscle of the final "toe-off" push in walking, running and jumping, and it supports the medial longitudinal arch by acting like a bowstring under the sustentaculum. Ballet dancers depend on it en pointe.
Anatomy
- Origin
Inferior two-thirds of the posterior surface of the fibula and the interosseous membrane.
- Insertion
Plantar base of the distal phalanx of the great toe.
- Action
Flexion of the hallux; plantarflexion of the ankle; supports the medial arch.
- Innervation
Tibial nerve.
- Nerve roots
S2–S3
- Arterial supply
Fibular artery.
- Relations
The most posterior tendon behind the medial malleolus. It grooves the posterior talus and passes under the sustentaculum tali.
Function
- Flexes the great toe (all joints)
- Push-off in gait
- Supports the medial longitudinal arch
- Assists plantarflexion and inversion
Clinical significance
Dancer's tendinitis
Stenosing tenosynovitis of FHL in its fibro-osseous tunnel behind the talus, in ballet dancers (en pointe). It causes posteromedial ankle pain and sometimes triggering of the hallux. It is often associated with an os trigonum (posterior impingement).
Compiled from standard anatomy and physiology references — see the Muscular System sources. For education only; not medical advice.