Had a half-knee done almost 3yrs ago (inside knee only).
Pros - almost completely pain free, tho my other knee maybe takes my mind off it if I do anything too strenuous, the whole thing nowhere near as bad/serious as I expected. Took 6-9months to feel good, but instantly better than it was.

Cons - you need to start the rehab as early as you can, I left it 3weeks until the swelling had gone down & the muscle had deteriorated, to be honest it’s never got back to where it used to be (but that could be age too).

My other knee is “going”, & I’ll get it done without hesitation if it gets anywhere near as bad as the first one.
That was like instant Tourette’s when it went & stopped me dead - the tipping point was crossing a road when a bus came & I just resigned myself to being run over because I couldn’t move fast enough.