Musculus flexor digitorum longus

Musculus

flexor digitorum longus

Caption: The

muscles of the anterior compartment of the lower leg are generally responsible for dorsiflexion, and the muscles of the posterior compartment of the lower leg are generally responsible for plantar flexion. The lateral and medial muscles in both compartments invert, evert, and rotate the foot.URL: https://cnx.org/contents/FPtK1zmh@8.108:y9_gDy74@5/Appendicular-Muscles-of-the-Pe Other versions:

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The flexor digitorum longus (FDL) muscle is located on the tibial side of the leg within the deep posterior compartment of the leg. At its origin it is thin but as it descends, the muscle increases in size.

Summary

origin: medial side of posterior surface of the tibia
insertion: plantar surfaces of bases of distal phalanges of the lateral four toes
action: flexes lateral four toes
arterial supply: posterior tibial artery
innervation: tibial nerve

Gross anatomy

At its origin on the medial distal tibial shaft, it lies medial to the tibialis posterior tendon. The FDL tendon passes through the tarsal tunnel located behind the medial malleolus. It is accompanied by tendons of the tibialis posterior and flexor hallucis longus (FHL) tendons, each occupying a separate synovial-lined tendon sheath . It runs obliquely on the plantar aspect of the foot crossing from medial to lateral. It splits into four smaller tendons each attaching to the base of the distal phalanx of the 2 through 5 toes. As it courses obliquely across the foot, the FDL crosses the deeper placed FHL tendon at a point called the master knot of Henry .

The quadratus plantae muscle attaches onto the lateral aspect of the FDL tendon in the foot.

Variant anatomy

The accessory flexor digitorum longus muscle is an accessory muscle that can occur alongside the flexor digitorum longus muscle. It has a reported prevalence of 6-8% and more commonly occurs unilaterally .

Related pathology

FHL tenosynovitis can occur due to prolonged use requiring extreme or repetitive plantar flexion, e.g. in ballet dancers and marathon runners. Reported points of synovitis include the knot of Henry and the fibro-osseous tarsal tunnel causing pain on the plantar aspect and the posteromedial aspect of the ankle respectively .

The FDL tendon is used in the foot for tendon transfers to correct hammer toe deformities in rheumatoid arthritis .