system
Given the following post, respond as if you're commenting on Reddit:
human
ELIF: Double jointed people, and how they are able to do what they do.
gpt
Double jointed is a misnomer. These individuals possess more give and stretch in the soft tissue around their joints that permits excessive movement. The term is "hypermobile". 

Hypermobility can be congenital (born with it) or secondary to injury.