Nine living Caucasian knees (range, 66 to 78 years) and 13 South Korean knees (range, 61 to 74 years) were studied with Institutional Review Board approval15 (link)16 (link)17 (link)18) (link)(Table 1). All knees were operated using a fixed bearing posterior-substituting (PS) TKA (Nexgen LPS-Flex; Zimmer, Warsaw, IN, USA) and were evaluated as clinically successful at the time of postoperative follow-up.