1. Unusual flexibility of the joints or greater than the normal range of motion in a joint, allowing them to be bent or moved beyond their normal range of motion.

Hypermobility is often misused to describe extra movements as seen in a contortionist.

2. Increased range of the movement of joints, joint laxity, occurring normally in young children or as a result of disease; such as, Marfan's syndrome (disorder of connective tissue of musculoskeletal system or abnormal length of the limbs; especially the fingers and the toes) or Ehlers-Danlos syndrome (disorder of the connective tissue; such as, joints that bend too easily into extensions).
3. Excessive joint play (movement) which permits increased mobility.

The area where two bones meet is called a joint and all joints have a cavity containing a small amount of synovial fluid, which allows for movement.

The attached tendons, muscles, ligaments, and joint capsules hold the joints in their correct positions.

Looseness of these supporting structures allows a joint to have extra motion and often, even normal activities that put stress on loose joints will irritate them.

Hypermobility syndrome may include congenital hip dislocations; scoliosis (curvature of the spine); elbow, kneecap and/or shoulder dislocations; or frequent ankle or wrist sprains.