I was just thinking today how glad I am that I had both knees replaced. Its not great for a while afterwards but is sooo worth it. Unlike fernbergian, I found physio exercises to be counterproductive. I did them religiously after first knee op. Result--inflammation leading to adhesions. I needed a manipulation under anaesthetic. Second knee I was wiser and refused physio. I iced and elevated my knee and kept moving. Just walking about gradually increasing the amount and distance and incorporating stairs. At the 3 week follow up appointment my knee was bending very well. The physio was most put out. I'd checked the NICE guidance for efficacy of outcome for physio post knee replacement and found no evidence! At 6 months in the one study, the outcome was exactly the same for physio vs no physio. I also refused opioid medication after the second op and managed fine on paracetamol.
Key thing to remember after a knee replacement is that just as you can't bend a hose full of water, you can't bend a swollen knee. Check the Bonesmart website for lots of info from people who have had these ops.
Good luck. It really is worth it.