Have you ever seen a contortionist bend his or her body into a shape or position that looks impossible? Perhaps you have a friend who can bend a body part into a position that seems like it would cause excruciating pain? If so, you may have heard people say that they're able to do these things because they're “double-jointed."
Your body has many joints, or areas where two bones meet. At the joint, the ends of bones are covered in cartilage. This allows them to move without causing pain or damage. Connective tissues called ligaments help hold the bones together, and muscles attached to the bones by tendons contract and extend to create motion.
Your joints allow for a normal range of motion. For example, your knee joint allows your leg to bend and straighten at the knee. If an accident forces your knee past its normal range of motion, your joint may become dislocated, which results in a lot of pain when bones and their ligaments are separated by force.
Some people have joints that allow for a range of motion well beyond what most people are capable of. While we may call these people “double-jointed," that term is a bit misleading. These people don't actually have twice the number of joints that others do. Instead, they simply have a larger range of motion in their joints.
Rather than “double-jointed," experts call this condition joint hypermobility. People with joint hypermobility have ligaments and bone structures that allow a greater range of motion than most other people have. This is mainly the result of genetics, which means that you're more likely to have joint hypermobility if one or both of your parents have it.
Besides being able to amaze your friends or get a job with the circus, is there any benefit to joint hypermobility? Absolutely! If you're a musician or an athlete, joint hypermobility can help you gain a competitive advantage against others. Of course, you have to maintain your joint hypermobility through regular stretching and exercise or you'll likely lose some of your flexibility as you age.
Joint hypermobility doesn't come without its costs, though. People with joint hypermobility often have a higher chance of developing arthritis in their joints. Some people also find they're more vulnerable to injuries. People with joint hypermobility who experience chronic pain and discomfort may suffer from a condition doctors call hypermobility syndrome.