Tibial inserts and tibial femoral systems are provided for improved knee reconstruction systems. External rotation of a knee joint implant is enhanced by modifications to the post, providing a recess that allows clearance of the post against the corners of a box wall within the femoral component. The rotation provides for a more natural knee joint motion of the implant. The depth, size, and location of the post relief may be modified for certain applications to provide both improved rotational motion and constraint against undesirable motion of the knee.
