I have been very fortunate not to have knee injuries now. I did several years ago, but went to a really good sports medicine doc at UC Davis to check the fit of my bike. he spent about 3 hours playing with cleat position, seat position, stem height, length, cants, etc. The outcome is changed position, cant and shim in one shoe, and no knee pain. While I know this is not the "be all, end all" solution for you, you might want to check for fit, after surgery to make sure something in your position on the bike is not contributing to your pain.