My right patella was out of line, and it hurt like crazy but only at a certain point of motion. Unfortunately, that point of motion came into play in almost every sport I play. It took a long time (and a lot of limping about) before I figured out that it was a mal-track.

It was my chiropractor that hit it with his activator a couple of times and fixed it.

It came back out of track about a week later. So I started manipulating it with my hands until it popped back into place. I haven't had a problem with it since then.

I'm not kidding.
Now I play all of my sports at 100%. . . whatever 100% might be for my age.