A tibial tray system includes a tibial tray configured for attachment to a surgically-prepared surface of the proximal end of the tibia. The tibial tray includes a track disposed in a generally A-P direction. The tibial tray system also includes a spline configured to engage the track and to be positionable in at least one location along the track. The spline includes a bearing surface that is configured to contact a femoral component of the knee prosthesis to guide movement of the femoral component during extension and flexion of the knee.