A knee joint prosthesis includes a femoral component having an anterior side, a posterior side, a pair of laterally spaced condylar portions, and an intercondylar portion joining the condylar portions and including a recess. A cam surface is located adjacent the intercondylar recess on the anterior side of the femoral component and has a saddle shape that is defined by an at least substantially concave first radius of curvature and a convex third radius of curvature that is perpendicular to the concave first radius of curvature. The prosthesis also includes a tibial component including a platform having an upper surface that includes first and second laterally spaced concavities. Each concavity is adapted for receiving one condylar portion of the femoral component. The tibial component has a tibial post for reception in the intercondylar recess of the femoral component. The tibial post has a saddle shaped anterior cam surface that is complementary to the saddle shaped anterior cam surface of the femoral component and is defined by an at least substantially convex second radius of curvature and a concave fourth radius of curvature that is perpendicular to the convex second radius of curvature.