joint lock
A joint lock is a grappling technique involving manipulation of an opponent's joints in such a way that the joints reach their maximal degree of motion and hyperextension. These are common techniques in martial arts such as judo, Brazilian jiu-jitsu and sambo among others.
In judo these are referred to as, 関節技 kansetsu-waza, "joint locking technique", and in Chinese martial arts as 擒拿 (chin na or qinna), which literally means "catching and locking". In Korea these are referred to as 관절기(gwan-jerl-gi, joint skill) or 관절꺾기(gwan-jerl-kerk-gi, joint breaking).