Sue you must have gone to some of the same places I've been. I have taught that trick off and on for well over 30 years. It only takes 15 pounds of pressure to dislocate the knee. If you can't kick that hard you ptrobably can't walk. Thje best thing about it is the ankle kick and or shin scrape only works if the other person can feel the pain. But dislocate or worse the knee and even if the jerk is on drugs an can't feel it they can't chase after you very fast is the leg keeps folding up. No knee no support.