The extensor digitorum longus runs in the anterior leg alongside the tibialis anterior and EHL, its four tendons passing under the extensor retinaculum to reach the extensor expansions of the lesser toes. It is the primary extensor of the lateral four toes and a secondary ankle dorsiflexor. Its four tendons are clearly visible on the dorsal foot during toe extension and serve as landmarks for dorsal foot anatomy.
| Origin | Lateral condyle of the tibia, anterior fibular shaft, and interosseous membrane |
|---|---|
| Insertion | Extensor expansions of the lateral four toes, extending to the middle and distal phalanges |
| Nerve Supply | Deep peroneal nerve (L5, S1) |
| Blood Supply | Anterior tibial artery |
| Actions | Extension (dorsiflexion) of the lateral four toes; Dorsiflexion of the ankle; Assists in eversion of the foot |
|---|
It lifts the lesser toes during swing phase of gait to achieve ground clearance and produces the toe extension that is visible during the heel contact response as the anterior compartment muscles eccentrically decelerate plantarflexion.
EDL weakness from L5 radiculopathy or deep peroneal nerve palsy is usually associated with EHL and tibialis anterior weakness producing foot drop, as all three share the same nerve supply. Isolated EDL dysfunction is uncommon. The four EDL tendons are occasionally involved in extensor retinaculum tenosynovitis at the ankle.
The four EDL tendons are clearly visible and palpable on the dorsal foot during active toe extension, fanning out from the ankle toward the lateral four toes and easily traced to their extensor expansion insertions.
Inflammation of the EDL tendon sheaths under the extensor retinaculum producing dorsal ankle pain and crepitus with foot dorsiflexion and toe extension, from overuse in runners or shoe irritation.
