Have you seen anyone else? I saw one physio who said I would need a knee washout which I didn't fancy at all. Anyway I went and saw another physio who confirmed the first one's diagnosis (meniscal tear and possible loose body) but who had a dicky knee himself and didn't want a washout either. He did some work on my knee and gave me home exercises and a massage technique to use (graston therapy)
http://www.sciencebasedmedicine.org/index.php/the-graston-technique-inducing-microtrauma-with-instruments/
the guy is a realist and said that i didn't need the expensive tool, to use a spoon handle or bowl or anything hard and smooth that was the right shape.
I know have a 99% fully functioning knee again! I don't rule out needing surgery at some point in the future but not yet. At the worst I was walking with a stick, using lifts and escalators and had a tens machine on my knee all day. I can now run, walk my dogs over rough ground and do stairs without a thought.