Joint prosthesis having controlled rotation

A joint prosthesis system includes first and second components that are joinable to each other in a manner to inhibit the rotation of the second component relative to the first component. The prosthesis system includes a rotation-inhibiting mechanism that has at least circumferential groove formed in one of a portion of the first component and a portion of the second component and at least one rib formed on the other of the first component and the second component. In one embodiment the rib may be eccentric, and the groove and the rib are matable with each other upon mounting of the second component within the first component.