Dislocations involving the four ulnar carpometacarpal joints are rare. These complex dislocations are considered to be due to the application of a hyperflexion force on the metacarpal heads. In the present case, an indirect hyperextension force on the metacarpal bones created a lever-arm effect resulting in rupture of the firm ligament complex of the carpometacarpal joints, inducing complete dislocations of the second to fifth carpometacarpal joints.