Flexor Digitorum Longus Detail

musculus flexor digitorum longus detail

FDL is the primary flexor of the toe DIP joints and the toe analogue of FDP in the hand. Its tendon passes through the master knot of Henry in the plantar midfoot, where it crosses the FHL tendon.

Nerve: Tibial nerve (L5, S1) Blood Supply: Posterior tibial artery Region: Lower Leg

Anatomical Data

Origin, Insertion & Supply

Origin	Posterior surface of the tibia — medial to the vertical tibial line
Insertion	Bases of the distal phalanges of toes 2-5
Nerve Supply	Tibial nerve (L5, S1)
Blood Supply	Posterior tibial artery

Biomechanics

Function & Actions

Actions	Flexes the DIP joints of toes 2-5 — primary action; Assists PIP and MTP flexion; Plantarflexes the ankle; Supports the medial longitudinal arch

Clinical Relevance

Clinical Notes

FDL transfer to the tibialis posterior is the primary tendon transfer for Stage II PTTD (FDL to TP transfer). The master knot of Henry is the reference for this harvest site. FDL also provides the slips for the quadratus plantae to modify the flexion vector.

Palpation

Tested by resisted distal phalanx flexion of the lesser toes.

Pathology

Common Injuries & Conditions

FDL Transfer in Stage II PTTD

FDL tendon harvested at the master knot of Henry and transferred to the navicular to augment the failed tibialis posterior in Stage II flatfoot deformity.