Knee Pain

I have had sore knees for several years now. The pain started while I was doing a lot of train during basketball season. I was running 30 min. a day and running in basketball practice everyday and at the end of each day I did plyometrics (jumpping program). Some days I would stay in the gym for a couple extra hours to run shooting drills. I kept this up for a couple of months then my knees started to hurt (Just bellow the knee cap). I have been to a sports injury professional (knee specialist) and had many X-rays. They found nothing, but my knee’s still hurt after a run or if I’m on my feet for a long period of time. Can some please help.