What does double-jointed mean?

Question

How are people who are double jointed physically different from everyone else?

Answer 1

Its just that people who are double jointed can hyperextend certain points of their body. It helps them reach further or kick faster depending on what joint you can hyper extend.  

Answer 2

They have loose tendons

Answer 3

It just means that they have loose tendons which allows them to bend their body parts in more extreme positions.

Answer 4

it means that you can bend yur body in ways other people cant like pop out a bone on purpose.