Today's medical appointment was the orthopedist, who took a fresh set of X-rays of my knees, and upon examining them, more or less said "Your knees are fucked." The cartilage in my knees is breaking down due to traumatic arthritis, and there's not a whole heck of a lot that can be done about it. As a temporary measure to try to reduce pain and inflammation, he gave me a large shot of cortisone into my right knee, whereupon I promptly threw up my lunch a few minutes later (a reaction which completely mystifies me, because I've never had a nausea reaction to a shot before).
If the knee pain persists and is still present in six weeks (which I fully expect it will be), there's apparently a succession of progressively more drastic measures that can be taken. I assume that progression ends with total knee replacement.