Flexor Digitorum Longus Beneath The Skin, Plantar View

Description

Seen from the plantar aspect beneath the skin, the flexor digitorum longus (FDL) tendon enters the sole along the medial midfoot and courses distally toward the lateral four toes, where it divides into slips for the distal phalanges of digits II to V. Proximally, its muscular belly would be understood to lie high in the deep posterior compartment of the leg, continuing as a long tendon passing posterior to the medial malleolus before reaching the plantar foot. The tendon lies deep to the plantar aponeurosis and superficial to the plantar interossei, with the metatarsals and phalanges forming the bony framework deep to the tendinous bands. Quadratus plantae and the lumbricals are positioned to modify and originate from the FDL tendon, respectively, near the midfoot and metatarsophalangeal region. Clear tendon anatomy. FDL matters because it is both a toe flexor and a dynamic support for the longitudinal arches, and its relationship to adjacent structures is clinically specific: it traverses the tarsal tunnel with the tibialis posterior tendon, flexor hallucis longus tendon, tibial nerve, and posterior tibial vessels, a crowded corridor where swelling or tenosynovitis can produce tarsal tunnel syndrome. In the plantar midfoot, the crossing between FDL and flexor hallucis longus at the so-called knot of Henry is a frequent point of interest in tendon transfer and reconstruction, and it helps explain coupled toe motion during gait and after injury. For surgeons addressing stage II posterior tibial tendon dysfunction, the FDL transfer relies on recognizing these plantar relationships and the route of the tendon to the lesser toes. Use this plate for teaching plantar-layer dissections in gross anatomy and podiatric anatomy labs, and for illustrating operative reports or textbooks covering tarsal tunnel release, FDL tendon transfer, or midfoot biomechanics in sports medicine. It also suits patient-facing education when explaining tendonitis along the medial ankle and plantar midfoot. Anatomical accuracy verified by SciePro's Medical Advisory Board.