Revisiting this thread, and specifically this earlier post of mine --
IMNSHO, avoiding exertion is hardly going to help. My mom's been trying this non-exertion thing for ages -- she swims* because she doesn't like to feel sweaty -- and it's just not paying off one bit. I wouldn't be surprised if she becomes wheelchair-bound within five years. She would be the first of my parents' generation to do so, including both sides of my family and all of my in-laws.
* and "swims" means "paddle gently from one end of the pool to the other", according to my sister, who's accompanied Mom on some of her pool sessions while I go to the weight room.
So my mom had her first knee replacement surgery just over two weeks ago. She'll probably need her other knee and one hip done sometime soon, too.
The one thing that's made her recovery less than a month long (maybe; she's still not back at the house) is the fact that mom n' dad's house has a lot of stairs. The bedroom and bathroom are upstairs, then there's the main level with kitchen etc, then the laundry and shower are in the basement. If it weren't for all those stairs, she'd have a lot less leg strength than she does now.
Like I said earlier, though, her now-habitual lack of exertion, especially after years of avoiding load-bearing exercise, is coming back to bite her. Also, if it wasn't for her physical therapist being so adamant about regaining her knee's range of motion, she'd probably end up letting her leg heal in a rigid, straight line since she would rather avoid any discomfort.
I think the four things that used to get her moving in the last decade were visiting her granddaughter, walking the dog, playing in music groups, and going to the YMCA. Now that the granddaughter has moved away and the dog has passed, she's got a lot of time to sit at home and dink around on the computer. Whatever gains she made after fixing her diet (got diagnosed with Type 2 diabetes) seem to be going away.
The good thing, potentially, is, based on comments from all her friends who also had knee replacements, she'll soon be walking easier than she had been in a long time. But, man, the recovery is taking a lot longer than anyone expected.