Flexor digitorum profundus tendon

At the level of the distal third of the forearm, the flexor digitorum profundus gives off a broad tendon. This crosses the superficial surface of the pronator quadratus and enters the hand by passing beneath the flexor retinaculum. Upon entering the hand, the tendon of flexor digitorum profundus splits into four slips that attach to the palmar surfaces of the bases of the distal phalanges of digits 2-5. The muscle fibers are arranged in a way that the medial part of the muscle inserts into digits 4 and 5, while the lateral part inserts to digits 2 and 3.

At the level of the finters, each flexor digitorum profundus (FDP) tendon, is deeper to the flexor digitorum superficialis (FDS) tendon up to the level of the distal A2 pulley, where the flexor digitorum superficialis (FDS) splits into radial and ulnar slips that rotate around the FDP tendon to become deep to the tendon.