No I'm not old or obese, but after I play tennis my tennis kill me. It may be the jarring running back and forth to get the ball, which is probably why I spend 99% of the time at the baseline, unless I have to come to the ball. I cross train with powerlifting and my knees have never heard from doing heavy deadlifts and squats. Any ideas? I lift twice a week and play tennis for 2 hours about 4-5 times a week.