Yesterday I was rolling, being the uke in a kata [Though it was no-gi bjj] Anyway, it was a sub being performed. The submission mainly arises from a rotation of your kness. Ok, now just lie down, with your left knee up. Now turn your lower leg clock wise, just as a clock hand would. It was not a Heek hook(HH damages mainly ACL). What did it damage? The problem was that when the person did it, I did not feel discomfort. There was a stretch, but no discomfort[shld you tap where there is no discomfort?]. However I woke up with an ache till now. No pain and can walk properly still tho.