Accessory flexor digitorum longus muscle

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The accessory flexor digitorum longus muscle is an accessory muscle in the deep posterior compartment of the leg with a reported prevalence of 6-8%. Unilateral muscles are more common although bilateral cases have been reported.

Summary

origin: variable; either the medial margin of the tibia and deep posterior compartment fascia; or the fibula
insertion: variable; either the quadratus plantae, tendon of flexor digitorum longus or both

Gross anatomy

The accessory flexor digitorum longus muscle arises from the medial margin of the tibia and the deep posterior compartment fascia or from the fibula. Its insertion may occur into the quadratus plantae muscle, tendon of flexor digitorum longus or both.

Related pathology

The accessory flexor digitorum longus muscle may compress the neurovascular bundle within the tarsal tunnel and cause tarsal tunnel syndrome . The accessory flexor digitorum longus muscle has also been reported to contribute to the development of flexor hallucis longus tenosynovitis .