A joint prosthesis system has two implant components and a bearing. One of the implant components has an articulation surface for articulation with the bearing. The other implant component has a mounting surface for supporting the bearing. At least one of the first and second components includes a recess and a stud in the recess. The joint prosthesis also includes an extension mounted on the stud and extending out from the bone-engaging surface to an end. Part of the extension is received in the recess.
