Everyone knows someone who can bend their fingers backward, put their legs behind their head, or easily twist themselves into the most difficult positions in yoga class. But what’s does it really mean when someone is “double-jointed”? For the scoop on the good, the bad, and the downright weird, we spoke with two joint health experts who know the topic well.
The first thing to understand, says Alice Chen, MD, a physiatrist at the Hospital for Special Surgery in New York City, is that double-jointed isn’t a medical term. Doctors and physical therapists tend to use the word hypermobile to describe people whose joints bend past the normal point of restriction.
Second, says Dr. Chen, hypermobility can leave people vulnerable to injuries—both in-the-moment and long-term. “The purpose of the joint is to give motion, but it’s also to prevent hypermotion, or motion in the wrong direction,” she says.
“When you take a step, your knee joint bends and extends so you have a stable point to put pressure on,” she continues. “If your knee joint went in both directions, it would collapse and you wouldn’t be able to bear weight.”
People who have hypermobility may find that their joints go past that safe and stable point, she adds, which can cause extra wear and tear on the cartilage and ligaments around the joint.
David Borenstein, MD, clinical professor of medicine at George Washington University and Master member of the American College of Rheumatology, says that hypermobility may not be a problem when people are young—and in fact, it may give them a physical advantage in some areas, like dancing and gymnastics.
“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,” says Dr. Bornstein. “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. Chen agrees. “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.”
There are different kinds of hypermobility, with different causes. Some people are just naturally more flexible than others. In other cases, a joint could become extra bendable after an injury or surgery to remove a damaged ligament. And occasionally, hypermobility is caused by a genetic disorder like Ehlers-Danlos syndrome, in which the body’s connective tissue isn’t as strong as it should be.
If you have hypermobility but haven’t experienced any pain or functional issues, Dr. Chen says it’s not necessary to see a doctor about it. (There’s one exception: Ehlers-Danlos syndrome can have other serious health risks, so if you have other symptoms such as easily bruised or abnormally stretchy skin, get it checked out.)
But she does recommend avoiding situations that stretch ligaments and extend joints beyond normal range—especially in weight-bearing situations—and being careful not to overstretch in activities like yoga.
It’s also very important for hypermobile people to build up muscle around their joints, says Dr. Chen. “When I have patients who are very flexible, they need to be even stronger than their counterparts with normal joints,” she says. “Their muscles need to protect and support their joints when they’re moving.”
That’s what she tells parents who are worried about their double-jointed children, as well. “If you can teach kids early enough and encourage them to do healthy cross-training and strength building, they will be less likely to have arthritic issues later in life,” she says.
Finally, she adds, people who are hypermobile in one direction are often tight in the other—like ballet dancers who can easily rotate their hips outward, but have a harder time rotating them inward. “Those are the patients we balance out with stretching,” she says, “but stretching in the direction they’re not used to going.”