A fixed-bearing prosthesis (10) ncludes 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 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.
