Various embodiments are directed to femoral and tibial bases that form structures of an implantable mechanical energy absorbing system. According to one embodiment, the bases include a low-profile body having a elongate and a curved body portion. One end of the base is elevated as compared to another end. An inner surface of the low-profile body has a raised portion extending along the elongate, straight portion of the low-profile body. The bases also include a plurality of openings positioned along the low-profile body for alignment and purposes of affixation to body anatomy.