A knee prosthesis system has a tibial component with frame with medial and lateral openings to receive the medial and lateral bearing components. The bearing components have distal surfaces that are exposed when assembled with the frame and pegs extending distally from the distal surfaces. The system optionally includes a tibial base plate with elongated curved receptacles to receive the pegs and allow the frame and bearing component assembly to rotate when mounted on the base plate. Different thicknesses of bearing components can be selectively locked onto the frame. Different sizes of tibial components have commonly sized, shaped and positioned elements so that multiple sizes of tibial components can be mounted on the same prepared tibial surface.
