A fixed-bearing prosthesis (10) includes a femoral component (12) having a medial condyle surface (32) and a lateral condyle surface (30). The knee prosthesis also includes a bearing (16) having a medial bearing surface (28) configured to articulate with the medial condyle surface of the femoral component, and a lateral bearing surface (26) configured to articulate with the lateral condyle surface of the femoral component. A tibial tray (14) is secured to the bearing. The tibial tray has a platform (18) with an elongated stem (20) extending downwardly from a lower surface (22) thereof. A posterior buttress (44) extends along a posterior section (50) of the perimeter of the trays platform, and an anterior buttress (64) extends along an anterior section (70) of the perimeter of the trays platform. Differently-sized tibial trays are interchangeable with differently-sized bearings.
