I used to have patella tendinopathy in one of my knees from heavy squats. I was able to eliminate all pain in about a week or two using these "Voodoo Floss Band" things.[1] They don't seem like they would work that effectively, but calling them magical is as justified as it was for the iPad. I had tried other strategies such as decline boards and negatives for several months which are commonly prescribed by physical therapists but they didn't make much of a difference. After my knees were 100% from the bands, I began squatting heavy weights again and focused more on keeping my knees out and my butt further back. This seems to have resolved my issues and I no longer experience knee pain squatting (my 1RM is >350).

1: http://www.mobilitywod.com/2012/05/voodoo-band-your-patella-...