My dad just had his knee replaced in February. He had a hard time with the therapy, they wanted him to bend to 115* and anything after 95 was a struggle. But, in his case, the doctor did a lot of work straightening his leg back out to normal. (His leg had really bowed out) Now he is done with the therapy, and things are pretty good overall. My dad will be 70 next week and he doesn't ride a bike so I am not much help there. He did admit last week that the new knee didn't seem to bother him much, but his other knee is really bad, his hips are shot, and his back is shot so I think they hurt him now and the new knee isn't as painful.

All of his joints are bone on bone and he waited too long for repairs, so he was told that he would have a tougher recuperation time. If you saw his x-ray, his knee was pretty much a flat line across the joint, where his femur rested on the shin bone, it was kind of wallowed out. Dad's was an extreme case and would be hard to compare.
My aunt had her knee replaced in October, and her knee wasn't as bad as my dad's and by Thanksgiving she was getting along pretty good. She did tell us in February that she could tell a difference when she didn't keep up the therapy, even in February, 6 months later. She also said that in the first 3 months she wondered if it was worth getting the replacement, but since then she realized that she wasn't waking up at night in pain, and then the question became, 'why did I wait so long'. She originally thought she would have to have both knees done, but now that she is walking better, (more evenly) the other knee doesn't hurt any more, so if they do anything at all to it, she may only have to get some cartilage replaced.
My point is that it will be rough at first, and therapy will stink, but I feel that if you give it time to heal properly you won't regret it. My dad doesn't seem to have any trouble with his leg after 4 months. He can do everything he could do before, (he could not bend his knee to 115* before the surgery, just for the record), and hopefully he will be able to get out and enjoy his car shows this summer.

As for my mom's sister, the only complaint now is that no one can keep up with her.
