Hypermobility (joints)

Hypermobility, also known as double-jointedness, describes joints that stretch farther than normal. For example, some hypermobile people can bend their thumbs backwards to their wrists, bend their knee joints backwards, put their leg behind the head, or perform other contortionist "tricks". It can affect one or more joints throughout the body.

Hypermobile joints are common and occur in about 10 to 25% of the population. Most have no other issues. In a minority of people, pain and other symptoms are present. This may be a sign of hypermobility spectrum disorder (HSD). In some cases, hypermobile joints are a feature of connective tissue disorders. One of these, Ehlers-Danlos Syndrome, was classified into several types which have been found to be genetic. Hypermobile Ehlers–Danlos syndrome (hEDS), formerly called EDS Type 3, remains the only EDS variant without a diagnostic DNA test.

In 2016 the diagnostic criteria for hEDS were re-written to be more restrictive, with the intent of narrowing the pool of hEDS patients, in the hope of making it easier to identify a common genetic mutation and create a diagnostic DNA test.

At the same time, joint hypermobility syndrome was renamed as hypermobility spectrum disorder, and redefined as a hypermobility disorder that does not meet the diagnostic criteria for any heritable Connective Tissue Disorder (such as hEDS, other types of Ehlers–Danlos Syndrome, Marfan Syndrome, Loeys–Dietz Syndrome, or osteogenesis imperfecta). Sometimes called "non-genetic EDS," hypermobility spectrum disorder can have the same signs as hEDS, but be caused not by a heritable genetic mutation but by problems in fetal development, such as pre-natal exposure to toxins like agricultural chemicals, drugs, or alcohol. Fetal Alcohol Spectrum Disorders affect at least 1 in 20 people in the U.S., and joint hypermobility with other symptoms is common.