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. Symptoms are often exacerbated during
pregnancy. 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 makes standing or walking difficult during pregnancy, so some women who have one of these disorders find they need to use a
wheelchair during pregnancy. Hypermobile joints are also relatively common among children, though this is often benign. 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. A shallow socket will lead to a relatively large range of movement. If the hip socket is particularly shallow, then the hip may dislocate easily.
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 produces 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. 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 ==