A prosthesis having: a) a first assembly with a first base portion to be placed against, and operatively secured to, a patients first bone and b) a second assembly with a second base portion to be placed against, and operatively secured to, a patients second bone. The first and second assemblies respectively define first and second surfaces that cooperate with each other to guide articulated movement between the first and second bones. At least one of the first and second base portions is configured to cooperate with a separate first component defining at least a part of one of the first and second surfaces to maintain the first component in an operative state. A second component is configured to define at least a part of the one of the first and second surfaces and can be placed in an operative state selectively in place of the first component.
