I had my left knee replaced back in aug of 2008 with great results. At the time I was having pain in both knees so much so my walking was severly limited. After the left knee was replaced i was able to walk much better with no pain in either knee. I am having the right knee replaced in Feb of 2013. The doctor told me both times that I would make the decision on when to have the knee surgery. And what he meant is when I could no longer live with the knee and how it affected my life. So at this point in time I can no longer walk and bend the right knee without pain so I made the decision to have it done. I never experienced back or sciatic pain due to the knee replacement. I also waited from the time I was 35(to young a different doc said) till I was 49 when I had the left knee replaced. I would have done it earlier as it gave me my life back. Good luck in whatever you decide.