Replacement !
I am an ex long distance runner who suffered with a bad knee for twenty years.
It finally got so bad, that I didn't want to walk any more, and three years ago had it replaced.
My goal was to be in a canoe a month after the operation, but I did a lot better, and was in my kayak a week after it.
I was amazed had how quick the recovery was, and should have done it years ago.
I now have no problem with stairs, and can hike mountains again, and it is just like I never had a knee problem
With that said; when I was in rehab, I noticed that all the people that had problems recouperating were the over weight ones
Jack L