 This post-market clinical follow-up study was designed to compile long-term knee replacement outcomes of the PFC Sigma fixed and PFC Sigma mobile Rotating Platform RP knee systems. The first patient had surgery on November 8, 2001 and the final patient had surgery on July 29, 2005. There were 120 knees consented by a single site, which was the planned sample size in the study protocol, with 117 receiving one of the study devices. The study was terminated as the primary outcome was met and the investigator decided to conduct the study without sponsor support after 2009. 