The invention relates to a joint prosthesis comprising a distal component (1) for anchoring to a first bone, a proximal component (2) for anchoring to a second bone, and a coupling piece (3) that, together with the first component (1), forms a flexion bearing around a first axis (34) and, together with the second component (2), forms a rotary bearing formed by the pin (31) and the bearing bush (32) around a second axis oriented transversely to the first axis (34). The rotary bearing comprises a multi-layer bearing insert (4), having a sliding sleeve (41) surrounding the pin (31) and a support sleeve (42) that encloses said sliding sleeve and is fastened to the coupling piece (3) by means of a securing element (5), wherein the securing element (5) comprises an actuation unit (52) within the support sleeve (42) and can be connected to the coupling piece (3) such as to ensure tensile strength by means of two aligned bores (47, 38) in the support sleeve (42) and the coupling piece (3).
