The Real Reason Some People Are Double-Jointed

Remember that kid on the playground who used to gross others out by bending his arm back way too far? Or the girl who could pull her fingers back all the way to the top of her wrist? Were you yourself one of those weirdos? In common parlance, we say that these people are double-jointed, but that term is kind of misleading. People who can bend their arms and legs farther than everyone else don't have more joints than people with a normal range of motion. Nor does it mean that they have twice the range of motion as the average Joe. According to Very Well Health, this is called joint hypermobility. To put it medically, it's "abnormally increased mobility of small and large joints beyond the limits of their physiological movement," and it is prevalent in around 5 percent of healthy adults. It's also more common in females than males.

So, if it's not because these people have an extra joint in their elbows allowing their arms to bend beyond reason, what are the causes of joint hypermobility? And also, is it dangerous? Should double-jointed people refrain from hyperextending the joints that are hypermobile? What kinds of medical issues could arise from this condition? Let's take a look into the causes of joint hypermobility, its effects on the human body, and how to deal with any problems it may create.

Very Well Health lists several factors that can lead to a person having hypermobility in their joints. The most salient of these may be simple genetics. Inherited traits like abnormal collagen or shallow joint sockets can cause joint hypermobility. Gender is also a factor. As state above, women are more likely to be double-jointed than men. Impairment to the nervous system can cause a person to have poor muscle tone, which ends up allowing for a wider range of joint movement. There's also something called proprioception, which, according to Sports Health, is "the body's ability to perceive its own position in space." People in whom this ability is abnormal may not be able to feel that their joints are being hyperextended. Medical conditions like Marfan syndrome, Down syndrome, and Ehlers-Danlos syndrome can cause it. And people who suffer from osteogenesis imperfecta can also have joint hypermobility. According to Medline Plus, this disorder affects the body's ability to produce collagen, which leads to brittle bones and weaker ligaments.

According to Versus Arthritis, age plays a role, as well. People tend to be more flexible when younger, so hypermobile people are even more hypermobile earlier in life. As they get older, the collagen in their ligaments binds together, getting stiffer and making them less flexible. This is why stretching becomes more uncomfortable with age. Physical activities like yoga and gymnastics can also lead to joint hypermobility.

Although younger people with joint hypermobility may not complain of any pain or discomfort, over time the hyperextension of the joint can end up causing problems. Rheumatologist David Borenstein, MD, told Real Simple that hypermobile people tend to not complain of joint pain when they're young. Some, in fact, can use it to their advantage, for example, in gymnastics or dancing. "But when you ask those people in 10, 20, 30 years later how they're feeling, it's not infrequent that those individuals have joint troubles," he said. "Either they stretched their tendons so far that now they're aching, or they're experiencing some degeneration in their joints because their cartilage has seen more pressure than it normally would."

Dr. Alice Chen, MD, said she also sees this in her patients. "I get adults who say, 'I used to show off in elementary school and gross my teacher out by twisting my arms behind my back,'" she says. "And they're coming to me now because those joints are hurting them — they're ending up with early arthritis." She said that some people may have more flexibility in their joints naturally, and others might get that way as a result of an injury or surgery. She also said that people with joint hypermobility don't need to see a doctor unless they are experiencing pain, discomfort, or mobility issues, but it is important to keep the muscles around hypermobile joints strong in order to support the joint.