Closed rupture of flexor digitorum profundus in zone III.

Closed ruptures of the flexor digitorum profundus (FDP) tendon cause a loss of active flexion at the distal interphalangeal joint. Commonly referred to as a 'jersey finger' because of its association with tackling sports, the distal aspect of FDP is avulsed from its insertion on the distal phalanx in zone I, with or without a fragment of bone. Because of this classic injury mechanism and pattern, providers may not seek advanced imaging beyond plain radiographs. Although rare, injury to FDP more proximally may occur. More often this injury is associated with a weak underlying tendon because of repetitive microtrauma or anomalous anatomy, for example. We present a case of a closed rupture of the FDP in zone III, and stress the importance of maintaining a high clinical suspicion and the potential use of adjunct ultrasound imaging to localise the site of injury.