The isolated traumatic dislocation of the triquetrum is an extremely rare injury. The clinical signs are unspecific. Roentgenograms of the wrist in posteroanterior and lateral views, possibly complemented by oblique views, will help to provide the diagnosis. The best therapy appears to be the open reduction and fixation with Kirschner wires. With the presented case report, the difficulties in using the classification carpal injuries are discussed. Finally, corresponding to the carpus ring theory, the plausibility of additional injuries to carpal ligaments in such trauma is pointed out.