No, You’re Not Double-Jointed!

by Lauren Tam

You’ve probably encountered a person showing off that they’re double-jointed.  Then, they proceed to show you what unusual shapes they can make with their limbs. You’re uninterested fairly quickly.  But what is interesting: they are not actually double-jointed. 

The term “double-jointed” implies that someone has twice the average number of joints, allowing them increased flexibility.  This is anatomically impossible.  In fact, you are not double-jointed but hypermobile.  It is the ability to move joints beyond their normal range of movement.  Hypermobility, also known as hyperlaxity, is most common in childhood and adolescence. It is also common in females and those of Asian and Afro-Caribbean descent.  Double-jointedness relates more to the soft tissues near the joints, rather than the actual joints themselves.  Joints are surrounded by ligaments, which connect bone to bone.  Similarly, tendons are what connect muscles to bone.  Everyone has the same range of motion, but the flexibility of a person’s ligaments or tendons determines natural flexibility.

Ball-and-Socket Joints

Though you can train it, you must be born with a certain flexibility to have hypermobility.  An explanation for this could be the bone shape and body composition.  The greatest flexibility is around the ball-and-socket joints.  A shallower indent leads to greater bendiness. These are joints like the shoulders, hips and arm. Double-jointed people sometimes have shallower joints that allow for a wider range of movement. 

Hypermobility Syndrome

20% of people are hypermobile.  Some people with shallow joints might find it easier to dislocate a joint. Unfortunately, there are some unpleasant symptoms such as pain and stiffness in the joints and muscles, clicking joints and thin or stretchy skin. If your hypermobility coincides with these symptoms, you may have joint hypermobility syndrome, or JHS.  JHS often runs in the family, causing changes in the collagen. Those who have elastic collagen might be more easily bruised or develop joint pains with greater frequency.  Additionally, weak collagen can make for loose and stretchy ligaments and joints. This would result in hyperextended joints. However, this is nothing to worry about unless it creates significant pain or recurring injuries.  

So, next time you’re at a post-COVID party, shut down those braggers with your superior knowledge.  Just try not to ruin the mood.