I'm not a body builder, just a 30 yr old male trying to stay fit and active. This past December i suffered an injury to my right knee, I have since been diagnosed with patellar tendonosis. It is a very nagging injury and I since have tried multiple different physical therapy sessions and have had little to no success. Everything that I have read points to building core strength. I was doing cardio 4-5x a week and playing football racquetball and softball before the injury. I'm now doing nothing but softball. I can't really run for extended periods without pain. I'm having major problems with weight gain and stress now from my lack of excercise. It's killing me... Can someone help with a startin point for building core strength with little stress on the knees ? Any experience anyone has please share.