A prosthetic system is provided for implantation into a body joint, such as a knee joint compartment between a femoral condyle and its corresponding tibial plateau. The prosthetic system includes a tibial component arranged to be fixed to the tibial plateau and having a top face including a generally flat surface and an opposed bottom face. The prosthetic system further includes a mensical component having a generally elliptical shape in plan, the mensical component having a top face and an opposed bottom face including a generally flat surface. The mensical component bottom face is arranged to engages the tibial component top face to form the assembled prosthetic system, where the mensical component is movable with respect to the tibial component.