 The secondary objectives of this investigation are:To evaluate the performance of the P.F.C. Sigma and P.F.C. Sigma Rotating Platform total knee systems in clinical practice. To evaluate the impact of patellar resurfacing on the performance of the P.F.C. Sigma and the P.F.C. Sigma Rotating Platform total knee systems. To evaluate the impact of Posterior Cruciate Ligament PCL sacrifice or retention on the performance of the P.F.C. Sigma and the P.F.C. Sigma Rotating Platform total knee systems. 