Figure 6.

Mallet finger injuries occur after forced flexion of the distal interphalangeal (DIP) joint during active joint extension. The “mallet” appearance of the finger results from the avulsion of the terminal extensor tendon and the resultant loss of continuity of the extensor mechanism, leading to the loss of active DIP extension and (a) the classic flexed posture at the DIP joint due to the unopposed pull of the flexor digitorum profundus (FDP) tendon. (B) Lateral view plain-film radiograph of a swan-neck deformity, as demonstrated by DIP flexion and proximal interphalangeal (PIP) hyperextension, secondary to a chronic mallet injury.