Yeah, it's probably just not completely healing if it's some sort of small injury, or it isn't strengthening completely if it's some sort of weakness problem, and when you use it more and more, that just delays the process...I'm not gonna tell you to stop training for a while, because I know I wouldn't do that either, but you should definitely try to drill the simplest movements, and stay away from drops. Question: does it hurt if you sit in the bottom of a squat position? In other words, if you drilled rolls for 20 minutes, would your knees be sore/aggravated from being consistently bent?