Why are some people double-jointed?

There’s always one in a group: the ‘double-jointed’ person who can bend their thumbs back to touch their wrists, or wrap their legs behind their head. We often think of these people as especially flexible, and sometimes they are. But often hypermobile joints are indicative of an underlying medical condition.

Hypermobility syndrome (HMS) is a combination of genetic conditions that lead to muscles, tendons and ligaments that are formed differently, and are usually more fragile and prone to injury. Benign joint hypermobility syndrome (BJHS) can be considered a low level of hypermobility where ‘bendy’ joints can result in some pain but no life-threatening complications. Marfan syndrome, on the other hand, can be much more serious: in addition to limb dislocation, sufferers of the more serious form can experience problems with their vision, nervous system and potentially fatal heart problems, all as a result of weakened connective tissues.

Clinical diagnosis of hypermobility syndrome is made using the Beighton score, a nine-point criteria that requires the suspected HMS patient to attempt certain postures and thus confirm or rule out certain conditions. Treatment might include pain-killing drugs, although a high level of fitness and a healthy lifestyle will often help in milder cases.