Knee prosthesis with a rotatable tibial bearing having a keyed axial securement

A joint prosthesis system includes first and second components that are joinable to one another in a manner to permit axial rotation of one component relative to the other component while achieving axial securement of the two components. In one embodiment the joint prosthesis system is a knee joint prosthesis and the two components are a tibial tray and a tibial bearing insert. The tibial bearing insert includes a mating stem that has one or more positive surface features on its exterior surface. The positive surface features mate with axial slot(s) formed in a mating cavity of the tibial tray to enable insertion of the mating stem within the mating cavity. Upon insertion the positive surface features are engaged by a circumferential groove disposed distally of the axial slot(s). Misalignment of the positive surface features and the axial slot(s) enables proper orientation of the tibial tray and tibial bearing insert, and provides axial securement of the two components.