I only saw the knee thing in your post the first time, but yes, we learned the wrist thing too. The instructor always picked me to practice on (so he could molest me). He was really into S & M and especially enjoyed doing the carotid restraint on me.
After doing the arm restraint on a guy who decided to pull a knife on me, I decided to put thumb on the point behind the jaw, and fingers along the underside of his jaw, push, and grip hard.
He quit struggling, and he quit bothering me after that.
Never did get formal training in anything.