An improved sliding patellar replacement component is provided. Various combinations of translational and/or rotational degrees of freedom are provided by boss and channel configurations between the base subcomponent of the replacement component and the articulating subcomponent of the patellar replacement component. In one embodiment, spin about one axis is restricted by a spin stop that may be movable to allow for ease of assembly. Alternatively, the boss and channel are configured to function as a spin stop. Assembly of the patellar replacement component in one embodiment is simplified by the provision of a boss assembly region.