Nothing. Realistically I can do nothing. For more reasons than I care to elaborate on, there is nothing that I could be doing that I am not already doing.
I'd like to start jogging again, but between the fact that my knees are one good run away from not being able to support my weight and there are no sidewalks where I live.
We tried on and off to get a treadmill but by the time we got one that I could use... Well, the first time I had a lasp on my use of it it got folded up and put somewhere where I couldn't use it, then thrown out for "taking too much space with no one using it" despite my constantly asking about getting it put back up so I could use it.
A couple of years ago I got one of those "body cycles" that you put on the floor and pedal but by then my legs were too bad for it... Despite them being advertised as low impact exercise. I try to use it when I can but twenty minutes is three days of pain.
Immortal body fixes most of those problems. Can't destroy immortal knees. And lots of places that are considered unsafe to go jogging are safer when you literally can't die.