The need to critically evaluate the efficacy of current total knee replacement (TKR) wear testing methodologies is great. Proposed international standards for TKR wear simulation have been drafted, yet their validity continues to be debated. The “gold standard” to which all wear testing methodologies should be compared is the measured in vivo TKR performance of the patient population. With the exception of retrieval analyses, few detailed comparisons of in-vitro vs. in-vivo TKR performance have been performed to date. The current study compares simulator TKR wear testing kinematics to measured in vivo TKR kinematics to evaluate the validity of the proposed ISO force-controlled wear testing methodology.