I've got what they call bilateral condromalasia patella. (not sure on the spelling, but it's close enough) It's both knees. They wanted to operate on them while I was stationed in the Philippines back in 1976. I talked to a lot of guys that had it done and they all said IF I could avoid it, put it off as long as possible.

Needless to say, I have and it doesn't pop up to often, but when it does I almost fall down. I might have to get it fixed one of these days, just don't know for sure. For the most part I do ok.