Recurrent dislocation of the pisiform bone.

A 17-year-old man had chronic pain and recurrent radial dislocation of the pisiform bone following a fall on his outstretched arm. The bone was excised, along with a 3 x 4-mm osteocartilaginous fragment from the distal triquetrum. Pisotriquetral joint instability should be considered in the differential diagnosis of palmar-ulnar wrist pain.