A tibial insert includes a base and a post extending from the base along a longitudinal axis. The post has a medial surface, a lateral surface, and a height along the longitudinal axis. The medial surface has a medial section, and the lateral surface has a lateral section oriented substantially parallel to the medial section. The medial section and the lateral section each have a width in a substantially anterior-posterior direction that is sufficient to enable varus/valgus constraint over a flexion/extension range from extension to about 90 to 120 degrees of flexion when the tibial insert is mated with a femoral component. The tibial insert further configured such that the medial bearing surface extends further in an inferior direction than the lateral bearing surface and a bottom point of the medial bearing surface is disposed closer to an anterior end portion of the medial bearing surface than a posterior end portion of the medial bearing surface.