The joint prosthesis has flexion hinge which is formed by a hinge fork and a pivot pin. The pivot pin is divided into shaft stubs (42,43) that are expanded for insertion in a coupling piece in retracted mounting position and are aligned with hinge bores of hinge fork in an expanded position. The pivot pin is provided with two bearing regions (41) at both ends. An intermediate joining region (40) is formed by bearing region along an axially extending plane, such that the casing of pivot pin is intersected at two points.
