Patellar Tendonitis (tendinosis?)

[Babw]

Any idea how to get rid of this? It's pretty much affecting my life as in the sports I've played for ever are becoming less and less frequent as I have to allow the knee pain to ease before taking part.

History of Osgood Schlatters in my teens, played too much sports and was advise to give up cricket (fast bowling) which I did. Now in my late twenties tennis, athletics or football seem to flare it up to an extent where I can't even walk down stairs.