"Double jointed" is a term used to describe people who are very flexible. They really only have one joint but the motion at that joint is more than what most people have."Double jointed" is a term used to describe people who are very flexible. They really only have one joint but the motion at that joint is more than what most people have.

You may have seen people in the circus or on TV who can support their body weight on their hands while wrapping their legs over their shoulders. Or contortionists who can get their entire body into a two foot square box. These people have hypermobile joints. They are often very thin, so the muscle bulk doesn't limit motion when the legs or arms are bent.

The contractile tissue around the joint is also loose or lax so the joint has more "give" or motion. You may have just one hypermobile joint. But many people who can touch the thumb to the forearm have generalized hypermobility throughout the body. They can also touch the palms to the floor with the knees straight.