I developed Osgood Slatus in my left knee(bone grows too fast for tendon. alternatively look up)when I was about 13, just when I'd started riding for real. I was told to rest, but for a semi hyper-active kid that's pretty hard. Had problems on/off ever since. Playing basketball+etc probably hasn't helped, but recently it has gotten worse. I'm 31yo and 5"11. Been taking anti-inflammatory(Cuprofen+ works well, but not good to do so much of, of course)knee supports,etc. Saw my GP last thurs and they said short of knee replacement this would be a life long issue. Have exercises to do and an appointment with a physio.
It's good to read this thread, simultaneously, depressing as hell. All I know is it's a massively complicated subject. Rest, train, exercise, try new ideas/concepts (swimming?) and do what the physio advises to exactement and there is hope. I'm counting on it. Good luck and try to learn as much about it as possible.