I had my left one done a year ago. It's not as good as a healthy real knee but it's a lot better than what I had. I had been having trouble with my left knee for 16 years and there was nothing left to do but replace it. The first couple weeks are rough but it gets better the more you use it.
Do the recommended therapy then do some more. Also take the pain meds so you are able to push yourself to do more. Get yourself a stationary bicycle and start with the seat as high as possible and keep lowering it as you get more flexibility in the knee.