Modular joint prosthesis system

A modular joint prosthesis includes a tibial component that may be rotatable or non-rotatable. The system includes a tibial bearing insert having surface features, either male or female, that are able to be slidably mated to complementary surface features of another component. In one embodiment, the tibial component is non-rotatable and the surface features of the tibial bearing insert are slidably matable to complementary surface features of a tibial plateau. In another embodiment the tibial component is rotatable and the surface features of the tibial bearing insert are slidably matable to complementary surface features of a rotating platform base. The rotating platform base, in turn, is rotably mounted to a tibial plateau. The system may utilize a securing member to prevent translation motion between the tibial bearing insert and the tibial plateau or the tibial bearing insert and the rotatable platform base.