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 and 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.

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Quick Facts Other names, Specialty ...

Hypermobility
Other names	hyperlaxity, benign joints hypermobility syndrome (BJHS), hypermobility syndrome (HMS)[1]
Hypermobile fingers and thumb
Specialty	Rheumatology, Medical genetics

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Hypermobile joints are common and occur in about 10 to 25% of the population,^[2] but in a minority of people, pain and other symptoms are present. This may be a sign of hypermobility spectrum disorder (HSD). Hypermobile joints are a feature of genetic connective tissue disorders such as hypermobility spectrum disorder or Ehlers–Danlos syndromes (EDS). Until new diagnostic criteria were introduced, hypermobility syndrome was sometimes considered identical to hypermobile Ehlers–Danlos syndrome (hEDS), formerly called EDS Type 3. As no genetic test can distinguish the two conditions and because of the similarity of the diagnostic criteria and recommended treatments, many experts recommend they be recognized as the same condition until further research is undertaken.^[3][4]

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, hEDS being the only EDS variant without 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 hEDS, other types of Ehlers–Danlos Syndrome, or other heritable Connective Tissue Disorder (such as Marfan's, Loeys–Dietz, or osteogenesis imperfecta).

People with Joint Hypermobility Syndrome may develop other conditions caused by their unstable joints.^[5][6] These conditions include:

• Joint instability causing frequent sprains, tendinitis, or bursitis when doing activities that would not affect others
• Joint pain
• Early-onset osteoarthritis (as early as during teen years)
• Subluxations or dislocations, especially in the shoulder (severe limits on one's ability to push, pull, grasp, finger, reach, etc., is considered a disability by the US Social Security Administration)^[7]
• Knee pain
• Fatigue, even after short periods of exercise
• Back pain, prolapsed discs or spondylolisthesis
• Joints that make clicking noises (also a symptom of osteoarthritis)
• Susceptibility to whiplash
• Temporomandibular joint dysfunction, also known as TMD
• Increased nerve compression disorders (such as carpal tunnel syndrome)
• The ability of finger locking
• Poor response to anaesthetic or pain medication
• "Growing pains" as described in children in late afternoon or night

Hypermobility generally results from one or more of the following:

• Abnormally shaped ends of one or more bones at a joint
• A defect of Type 1 collagen (as found in Ehlers–Danlos syndrome) or other connective tissue (as found in Loeys–Dietz syndrome and Marfan syndrome) resulting in weakened ligaments/ligamentous laxity, muscles and tendons. This same defect also results in weakened bones, which may result in osteoporosis and fractures.
• Abnormal joint proprioception (an impaired ability to locate body parts in space and/or monitor an extended joint)

These abnormalities cause abnormal joint stress, meaning that the joints can wear out, leading to osteoarthritis.

The condition tends to run in families, suggesting a genetic basis for at least some forms of hypermobility. The term double jointed is often used to describe hypermobility; however, the name is a misnomer and should not be taken literally, as hypermobile joints are not doubled/extra in any sense.

Most people have hypermobility with no other symptoms. Approximately 5% of the healthy population have one or more hypermobile joints. However, people with "joint hypermobility syndrome" are subject to many difficulties. For example, their joints may be easily injured, be more prone to complete dislocation due to the weakly stabilized joint and they may develop problems from muscle fatigue (as muscles must work harder to compensate for weakness in the ligaments that support the joints). Hypermobility syndrome can lead to chronic pain or even disability in severe cases. Musical instrumentalists with hypermobile fingers may have difficulties when fingers collapse into the finger locking position. Or, conversely, they may display superior abilities due to their increased range of motion for fingering, such as in playing a violin or cello.^{[citation needed]}

Hypermobility may be symptomatic of a serious medical condition, such as Stickler syndrome, Ehlers–Danlos syndrome,^[12] Marfan syndrome,^[12] Loeys–Dietz syndrome, rheumatoid arthritis, osteogenesis imperfecta,^[12] lupus, polio, Fragile X syndrome, Down syndrome,^[12] Morquio syndrome, cleidocranial dysostosis or myotonia congenita.

Hypermobility has been associated with myalgic encephalomyelitis (chronic fatigue syndrome) and fibromyalgia. Hypermobility causes physical trauma (in the form of joint dislocations, joint subluxations, joint instability, sprains, etc.). These conditions often, in turn, cause physical and/or emotional trauma and are possible triggers for conditions such as fibromyalgia.^[13]

People with hypermobility may experience particular difficulties when pregnant. During pregnancy, the body releases relaxin and certain hormones that alter ligament physiology, easing the stretching needed to accommodate fetal growth as well as the birthing process. The combination of hypermobility and pregnancy-related pelvic girdle during pregnancy can be debilitating. The pregnant person with hypermobile joints will often be in significant pain as muscles and joints adapt to the pregnancy. Pain often inhibits such people from standing or walking during pregnancy. Some pregnant people who have one of these disorders find they need to use a bedpan and/or a wheelchair during pregnancy. Some may experience permanent disability. ^{[citation needed]}

Symptoms of hypermobility include a dull but intense pain around the knee and ankle joints and the soles of the feet. The pain and discomfort affecting these body parts can be alleviated by using custom orthoses.

Joint hypermobility syndrome shares symptoms with other conditions such as Marfan syndrome, Ehlers-Danlos Syndrome, and osteogenesis imperfecta. Experts in connective tissue disorders formally agreed that severe forms of Hypermobility Syndrome and mild forms of Ehlers-Danlos Syndrome Hypermobility Type are the same disorder. ^{[citation needed]}

Generalized hypermobility is a common feature in all these hereditary connective tissue disorders and many features overlap, but often features are present that enable differentiating these disorders.^[18] The inheritance pattern of Ehlers-Danlos syndrome varies by type. The arthrochalasia, classic, hypermobility and vascular forms usually have an autosomal dominant pattern of inheritance. Autosomal dominant inheritance occurs when one copy of a gene in each cell is sufficient to cause a disorder. In some cases, an affected person inherits the mutation from one affected parent. Other cases result from new (sporadic) gene mutations. Such cases can occur in people with no history of the disorder in their family.

The dermatosparaxis and kyphoscoliosis types of EDS and some cases of the classic and hypermobility forms, are inherited in an autosomal recessive pattern. In autosomal recessive inheritance, two copies of the gene in each cell are altered. Most often, both parents of an individual with an autosomal recessive disorder are carriers of one copy of the altered gene but do not show signs and symptoms of the disorder.

Hypermobile joints occur in about 10 to 25% of the population.^[2]

• Ligamentous laxity