The invention relates to an articular prosthesis comprising an articulation cavity (21) for an articulation body (15), in a head section (13) of a base part (11). The position of the articulation body (15) used in the articulation cavity (21) defines the subsequent collar axis for an articulation part mounted on the articulation body (15). The articulation cavity (21) has a tapered lateral surface (25) which co-operates with an articulation surface (43) that is symmetrical to a pivoting axis. Said articulation surface has a circular edge (43). In a cutting plane perpendicular to the pivoting axis (45), which passes through the contact point (55) between the lateral surface (25) and the circular edge (43), the radius (63) of the circular edge (43) is larger than the radius (65) at the apex of the cutting curve (61) between the cutting plane and the lateral surface (25). Two contact points can thus be created between the circular edge (43) and the lateral surface (25), said contact points being located on different sides of a plane containing the rotational axis (30) and the pivoting axis (45). In this way, a rolling movement of the articulation body (15) in the articulation cavity (21) is prevented.