Hypermobility (joints)

Hypermobility, also known as double-jointedness, describes joints that stretch farther than normal.^[2] 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.

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

Hypermobile joints are common and occur in about 10 to 25% of the population.^[3] 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.^[4], and joint hypermobility with other symptoms is common.^[5]

Signs and symptoms

People with joint hypermobility syndromes may develop conditions caused by their unstable joints.^[6][7] These conditions include:

• Subluxations or dislocations, especially in the shoulder
• Sprains, tendinitis, or bursitis from activities. However, a 2018 study reports that while hypermobile individuals are more likely to suffer dislocations doing sports than non-hypermotile individuals, they are less likely to suffer muscle and tendon sprains. The overall chances of sports injury are not significantly different.^[8]
• Joint pain
• Early-onset osteoarthritis
• Fatigue or muscle pain from chronically using muscles to hold hyperflexible joints in place
• 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
• Chance of nerve compression disorders in the joints (such as carpal tunnel syndrome)
• "Growing pains" (as described in children in late afternoon or night)

Associated conditions

Joint hypermobility may be associated with other conditions. These include ADHD, autism, dyspraxia, fibromyalgia, hereditary connective tissue disorders, mitral valve prolapse, and anxiety disorders such as panic disorder.^{[9][10][11][3][12]} Joint hypermobility does not cause these other conditions. Most people with joint hypermobility do not have them. In people who do, the underlying cause can be a general syndrome that affects the whole body and brain (such as Autism or Fetal Alcohol Spectrum Disorders), or a genetic condition or disease that affects certain tissues (such as Ehlers-Danlos syndrome or lupus).

Medical conditions that can cause joint hypermobility include FASDs, Stickler syndrome, Ehlers–Danlos syndrome,^[13] Marfan syndrome,^[13] Loeys–Dietz syndrome, rheumatoid arthritis, osteogenesis imperfecta,^[13] lupus, polio, Fragile X syndrome, Down syndrome,^[13] Morquio syndrome, cleidocranial dysostosis and myotonia congenita. All have other diagnostic criteria as well.

Causes

A hypermobile thumb (also called Hitchhiker's thumb)

Hypermobility generally results from one or more of the following:

• Unusually-shaped ends of one or more bones where they form a joint, or an increased angle of the bone, such as in coxa valga.
• A mutation in collagen or collagen-related genes (as found in certain types of Ehlers-Danlos syndrome) or other connective tissue (as found in Loeys–Dietz syndrome and Marfan syndrome) resulting in weakened ligaments/ligamentous laxity. Ligaments hold bones together at the joints.
• Abnormal joint proprioception (an impaired ability to locate body parts in space and/or monitor an extended joint)

Any of these causes can increase the level of mechanical stress on a joint. Chronically stressed joints may experience higher or faster than usual levels of wear, leading to osteoarthritis.

Hypermobility tends to run in families, suggesting a genetic basis for at least some forms. The term double jointed is often used to describe hypermobility; however, the name is a misnomer and should not be taken literally, as people with hypermobile joints do not have any extra joints, or any extra bones or parts in the joint.

Most people with hypermobile joints do not have a hypermobility spectrum disorder. Approximately 5% of the healthy population has one or more hypermobile joints. However, people with symptomatic hypermobility are subject to many difficulties. For example, their joints may be easily injured, be more prone to complete or partial 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 syndromes can lead to chronic pain or even disability in severe cases.

Hypermobility has been associated with myalgic encephalomyelitis (chronic fatigue syndrome) and fibromyalgia. Hypermobility syndromes can cause physical trauma, pain, and stress (in the form of joint dislocations, joint subluxations, joint instability, sprains, etc.), and chronic stress from repeated trauma is a possible trigger for chronic conditions such as fibromyalgia.^[14]

People with hypermobility syndromes 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 may 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. ^{[citation needed]}

Syndromes

Hypermobile metacarpo-phalangeal joints

Hyperextension of the thumb

Hyperextension of the hand

Hypermobility syndrome is generally considered to comprise hypermobility together with other symptoms, such as myalgia and arthralgia. It is relatively common among children and reported more often in females than males.

Current thinking suggests four causative factors:

• The shape of the ends of the bones—Some joints normally have a large range of movement, such as the shoulder and hip. Both are ball-and-socket joints. The joint ends of bones finish their growth last, so children tend to have more flexible joints than adults; children may "grow out of" hypermobility as their bone ends fully develop. But if a shallow rather than a deep socket is genetically inherited, or results from a problem in development, then a relatively large range of movement will be possible even as an adult. If the socket is particularly shallow, then the joint may dislocate easily.
• Ligament problems—The ligaments that hold bones together are made of several types of protein fiber. These proteins include elastin, which gives elasticity. Gymnasts and athletes can voluntarially acquire functional hypermobility in some joints by stretching healthy ligaments over time. However, weak or abnormally long ligaments can cause unstable hypermobile joints. Protein deficiencies may weaken ligaments. Some hormones alter the structure of collagen proteins. For example, in late pregnancy, relaxin allows the ligaments of the pelvis to lengthen so the head of the baby can pass. Hormone imbalances may contribute to hypermobility.
• Muscle tone—Opposing sets of muscles are attached to bones to move joints in various directions. The tone of muscles--a mild basic level of contraction that protects joints and organs--is controlled by the nervous system. Neuromuscular problems can cause loss of muscle tone, increasing the range of movement possible and removing the muscles' protection of the joint. Lack of exercise also weakens the muscles that support and anchor highly flexible joints such as the shoulder, hip, wrist, and ankle.
• Proprioception—Disorders such as dyspraxia affect the brain's communication with the sensors that detect the motion and position of the body in space. A person with poor proprioception or kinesthetic awareness may habitually hyperextend joints during normal activities such as walking and sitting, because they can't internally sense where the joint is. If stress/pain perception is also affected, they may not experience hyperextension as uncomfortable until an injury occurs.^[15]

Hypermobility can also be caused by genetic or developmental disorders that reduce the strength of the connective tissue the body can make. Commonly, hypermobility is dismissed by medical professionals as nonsignificant, though it may be a sign of a systemic problem.^[16]

Ehlers–Danlos syndrome hypermobility type

Joint hypermobility is often correlated with hypermobile Ehlers–Danlos syndrome (hEDS, known also by EDS type III or Ehlers–Danlos syndrome hypermobility type (EDS-HT)). Ehlers–Danlos syndrome is a genetic disorder caused by mutations or hereditary genes, but the genetic defect that produced hEDS is largely unknown. In conjunction with joint hypermobility, a common symptom for hEDS is smooth, velvety, and stretchy skin. When diagnosing hEDS, the Beighton Criteria are used, but are not always able to distinguish between joint hypermobility syndrome and hEDS.^[17]

Ehlers–Danlos hypermobility type can have severe musculoskeletal effects, including:

• Jaw laxity that may make an individual's jaw open and close like a hinge, as well as open further than the average.
• Neck pain that can lead to chronic headaches and is usually associated with a crackling or grinding sensation (crepitus).
• The spine may end up in a "round back" or inversely may extend too much into hyperlordosis. Individuals may also experience scoliosis.
• Joints commonly associated with hypermobility (wrists, knees, ankles, elbows, shoulders) may be at more severe risk to dislocate or strain.

Diagnosis

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]} The basic issue is that Ehlers-Danlos Syndrome was defined based on its observable symptoms in the skin and joints, but is now classified as a genetic disorder. However, it is impossible to tell whether a person has EDS symptoms due to an inherited EDS gene, a spontaneous mutation that causes identical symptoms, or a problem in fetal development causes identical symptoms, without both knowing the genetic family history and performing a specialized genetic test. The results do not matter to clinical treatment of the symptoms.

Generalized hypermobility is a common feature in 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.

Beighton criteria

Beighton score criteria: one point for each elbow and knee that hyperextends by 10 degrees or more (4 points), one for each little finger that bends back by 90 degrees (2 points), one for each thumb which can be touched to the forearm (2 points), and one for touching the floor with the palms.^[19]

As of July 2000, hypermobility was diagnosed using the Beighton criteria. In 2017, the criteria changed, but still involve the Beighton score.^[20] The Beighton criteria do not replace the Beighton score but instead use the previous score in conjunction with other symptoms and criteria. HMS is diagnosed in the presence of either two major criteria, one major and two minor criteria, or four minor criteria. The criteria are:

Major criteria

• A Beighton score of 5/9 or more (either current or historic)
• Arthralgia for more than three months in four or more joints

Minor criteria

• A Beighton score of 1, 2 or 3/9 (0, 1, 2 or 3 if aged 50+)
• Arthralgia (> 3 months) in one to three joints or back pain (> 3 months), spondylosis, spondylolysis/spondylolisthesis.
• Dislocation/subluxation in more than one joint, or in one joint on more than one occasion.
• Soft tissue rheumatism. > 3 lesions (e.g. epicondylitis, tenosynovitis, bursitis).
• Marfanoid habitus (tall, slim, span/height ratio >1.03, upper: lower segment ratio less than 0.89, arachnodactyly; positive Steinberg finger / Walker wrist signs).
• Abnormal skin: striae, hyperextensibility, thin skin, papyraceous scarring.

Beighton score

The Beighton score is an edited version of the Carter/Wilkinson scoring system which was used for many years as an indicator of widespread hyper-mobility. Medical professionals varied in their interpretations of the results; some accepting as low as 1/9 and some 4/9 as a diagnosis of HMS. Therefore, it was incorporated, with clearer guidelines, into the Beighton Criteria. The Beighton score is measured by adding 1 point for each of the following:

• Placing flat hands on the floor with straight legs
• Left knee bending backward
• Right knee bending backward
• Left elbow bending backward
• Right elbow bending backward
• Left thumb touching the forearm
• Right thumb touching the forearm
• Left little finger bending backward past 90 degrees
• Right little finger bending backward past 90 degrees

Beighton test in a person with a 9/9 score

The Beighton score has been widely used among athletes for screening purposes. It does not appear to be a valid scale when used for this purpose: there exists a statistically significant correlation between the score and the athlete's passive shoulder and hip ranges of motion, but the difference is small enough to be buried by measurement error.^[21]

Treatments

Physical therapy

It is important that hypermobile individuals remain fit – even more so than the average individual – to prevent recurrent injuries. Regular exercise and exercise that is supervised by a physician and physical therapist can reduce symptoms because strong muscles increase dynamic joint stability. Low-impact exercise such as closed kinetic chain exercises are usually recommended as they are less likely to cause injury when compared to high-impact exercise or contact sports.^[22]

Heat and cold treatment can help temporarily to relieve the pain of aching joints and muscles but does not address the underlying problems.

Medication

Medication is not the primary treatment for hypermobility, but can be used as an adjunct treatment for related joint pain. Nonsteroidal anti-inflammatory drugs are the primary medications of choice. Narcotics are not recommended for primary or long-term treatment and are reserved for short-term use after acute injury.

Lifestyle modification

For some people with hypermobility, lifestyle changes decrease symptom severity. In general, activity that increases pain is to be avoided. For example:

• Avoiding hyperextension
  • Typing can reduce pain from writing.
  • Voice control software or a more ergonomic keyboard can reduce pain from typing.
  • Bent knees or sitting can reduce pain from standing.
• Strength training to support weak joints with strong muscles
  • Weakened ligaments and muscles contribute to poor posture, which may contribute to other medical conditions.
  • Isometric exercise avoids hyperextension and contributes to strength.
  • Unwanted symptoms are frequently reduced by some forms of yoga
• Low-impact sports
  • Use of low impact elliptical trainer machines can replace high-impact running.
  • Pain-free swimming may require a kickboard or extra care to avoid hyperextending elbow and other joints.
  • Bike riding, especially on ergonomic recumbents.

Other treatments

• Bracing can be helpful for temporarily protecting unstable joints.
• Physical therapy

Epidemiology

Hypermobile joints occur in about 10 to 25% of the population, but do not define hypermobility syndromes.^[3]

See also

• Ligamentous laxity