Also known as hyper flexibility or double-jointedness, joint hypermobility refers to certain joints in the body that bend more than what is considered normal. These people are usually gynmasts or dancers, people who are "good" at yoga or those who try to fly under the radar but  get turned into walking freakshows by their friends who request to see the "cool" tricks they can pull off, like bending their fingers all the way back to touch their hand or being able to dislocate their shoulders.