The invention relates to a joint part prosthesis, particularly for a finger joint, consisting of either a proximal or a distal component, as well as a shaft that extends away from this component, to be mounted in a bone, which shaft is configured with a fin-like anti-twist device. According to the invention, it is provided that as an anti-twist device (7), at least two anti-twist elements (8) are disposed on the mantle surface (6) of the shaft (4), with rotation symmetry, and extend radially away from this mantle surface (6) and in the longitudinal direction of the shaft (4), whereby the distance of the anti-twist elements (8) from the mantle surface (6) decreases slightly in the direction toward the free end (5) of the shaft (4).