A knee joint prosthesis assembly can include a femoral component that has a medial and a lateral condyle portion connected by a patellar track portion. The femoral component can form an opening between the medial and lateral condyles. A tibial component can have a medial portion that includes a first engagement structure and a lateral portion that includes a second engagement structure. A medial bearing can have a third engagement structure formed thereon that selectively engages the first engagement structure. A lateral bearing separately formed and independent from the medial bearing can have a fourth engagement structure formed thereon that selectively engages the second engagement structure.
