Joint hypermobility syndrome is primarily caused by inherited variations in connective tissue structure and function, most notably involving collagen—the primary protein responsible for the strength and elasticity of ligaments and tendons. Individuals with joint hypermobility syndrome tend to have looser, more elastic connective tissue, which permits excessive joint movement but offers less stability. While hypermobility itself may be harmless or even advantageous in specific contexts, such as gymnastics or ballet, the syndrome refers to cases where hypermobility leads to chronic symptoms like pain, fatigue, and functional impairment.
The causes of joint hypermobility syndrome are complex and often linked to genetics, but other factors such as age, gender, ethnicity, and individual body makeup also influence it. Some people inherit joint laxity without symptoms. Others suffer disabling problems even with only mild flexibility. Knowing these causes helps doctors and patients detect the syndrome early and manage it well.
Genetic and Collagen Factors in Joint Hypermobility Syndrome
The most established cause of joint hypermobility syndrome is genetic. Many cases run in families, showing a clear genetic link. Several genes likely affect how collagen and elastin fibers form and organize in connective tissues. When these proteins are more elastic or less strong than normal, ligaments and tendons loosen.
Joint hypermobility syndrome is different from genetic disorders like Ehlers-Danlos syndrome (hypermobility type), but their symptoms can overlap. Ehlers-Danlos syndromes affect collagen production. Joint hypermobility syndrome may involve milder or different mutations that cause widespread symptoms without a full disorder diagnosis.
Multiple family members, especially close relatives, may show similar flexibility or joint problems. This suggests the syndrome follows an inherited pattern, possibly autosomal dominant or polygenic. However, no single gene has been pinpointed for joint hypermobility syndrome.
At the molecular level, abnormalities in type I and type III collagen play a major role. These collagens provide strength to ligaments, skin, and organs. When collagen is less dense or disorganized, tissues stretch more than usual. This causes:
- Greater joint range of motion
- Reduced joint stability
- Higher risk of sprains and dislocations
- More strain on muscles and tendons
Over time, overextension leads to joint wear, pain, and soft tissue damage. It can also cause proprioceptive problems, where the brain struggles to sense joint position, increasing injury risk.
In some people, other connective tissues like skin, blood vessels, and the gut lining show subtle changes. This explains symptoms like easy bruising, digestive problems, and nervous system issues seen in joint hypermobility syndrome.
How Age and Hormones Affect Causes of Joint Hypermobility Syndrome
Age is another important factor. Children and teens are naturally more flexible because their bodies are still growing. Usually, flexibility decreases with age as collagen stiffens and muscles strengthen. But in joint hypermobility syndrome, excess movement may persist or worsen.
Children with the syndrome often seem very “bendy.” Parents may notice tricks like bending thumbs back or unusual sitting positions. While these may seem harmless, many develop pain, fatigue, or coordination problems as they grow, especially during growth spurts.
Adults may find symptoms stay the same or get worse. Aging stiffens ligaments, which can ease symptoms for some. For others, years of joint strain cause pain and instability.
Gender also plays a role. Women are much more likely to have joint hypermobility syndrome than men, possibly three times more. This difference relates partly to collagen differences but also to hormones, especially estrogen.
Estrogen affects tissue elasticity. Its changes during menstrual cycles, pregnancy, or menopause can worsen joint instability. Pregnancy raises relaxin, a hormone that loosens ligaments for childbirth. This can increase back pain, pelvic pain, and even risks like early labor in women with the syndrome.
Understanding these hormonal effects helps doctors plan treatments with physiotherapy, hormone management, and support during key life stages.
