“I’m double-jointed!” That’s what my middle school classmate proudly proclaimed after demonstrating how she could bend her arm back in a way that made me wince.
Turns out, being “double-jointed” is not really a thing.
“Double joints aren’t real,” Dr. Maryellen Brucato, a board-certified foot and ankle surgeon, and podiatrist, told HuffPost. “You do not possess extra joints anywhere in your body. When someone describes themselves as ‘double-jointed,’ what they actually have is hypermobility.”
Hypermobility is when a person’s joints can move beyond the typical range of motion.
“You have the exact same skeletal framework as everyone else,” Brucato emphasised. “Your joints just stretch and move far beyond the typical baseline.”
So double-jointedness is not a medical diagnosis but rather a sort of nickname or layman’s term for hypermobility, or hypermobility spectrum disorders (HSD).
“I see patients every day who can bend their fingers backward, hyperextend their elbows or knees, or move their shoulders in ways that seem impossible to most people,” said Dr. Jacques Courseault, a physical medicine and rehabilitation physician, and assistant professor at Tulane University School of Medicine.
“They don’t have additional joints. Their joints simply have greater mobility because of differences in the connective tissues that support them.”
What exactly is hypermobility?
“When patients say they are double-jointed, it usually means that they are able to sublux their joints,” said Dr. Hunter Rafoth, a sports medicine physician for Orlando Health Jewett Orthopedic Institute. “What that means is you can pop a joint ‘out of socket’ on command and pop it back in.”
And hypermobility is not a particularly rare condition either.
“It’s much more common than people think, [impacting] somewhere around one in 10 to one in three people, depending on how you are measuring and what criteria you include,” said Dr. Nicholas Belasco, a sports medicine physician and expert for JustAnswer. “Doctors check for it with a quick test called the Beighton score. Can you bend your pinky back past 90 degrees, touch your thumb to your forearm, put your palms flat on the floor without bending your knee? There are nine points possible in total.”
So what exactly is happening in your body when you have hypermobility?
“Anatomically, it comes down to the integrity of your connective tissue,” Brucato said. “Ligaments are designed to act like strong cables that tether bones together and restrict excessive movement. In people who are considered ‘double-jointed,’ those soft tissues and collagen fibres are far more lax and stretchy than average. Because the ligaments don’t pull tight when they should, the joint can bend, hyperextend or rotate past normal anatomical limits.”
Xavier Lorenzo via Getty Images
So basically, connective tissue holds joints in place. And when it’s looser or stretchier than average, those joints move farther than expected.
“Most people think flexibility is primarily about muscles, but joint hypermobility is really an extracellular matrix issue … the structural framework that supports our tissues,” Courseault said.
“It includes collagen, elastin and other proteins that help determine how our connective tissues respond to mechanical forces. One of the most important components of this system is fascia, the continuous connective tissue network that surrounds, supports and connects our muscles, nerves, blood vessels and other structures throughout the body.”
Because fascia plays a major role in “transmitting forces, facilitating movement, and coordinating how different parts of the body function together,” the different mechanical properties involved in hypermobility result in people who can move their joints beyond typical limits.
“Your ligaments, tendons and the capsule around the joint are a bit looser and stretchier, so the joint just keeps going past where most people’s stop,” Belasco said. “The difference between someone with hypermobile joints vs. just enhanced flexibility comes down to the type of collagen you make. Hypermobile folks tend to have a mix that’s a little more elastic and a little less tough. Think rubber band versus shoelace.”
What causes hypermobility?
“Genetics play a major role,” Brucato said. “In many cases, hypermobility stems from inherited conditions that alter collagen – the primary protein that gives structure to our soft tissues. A notable example is Ehlers-Danlos syndrome (EDS), a genetic disorder that directly impacts collagen production and leads to widespread joint laxity.”
Hypermobility tends to run in families, and age can play a part as well.
“In one set of studies, roughly two-thirds of kids aged 4 to 7 counted as hypermobile, and by the early teens it was closer to 1 in 10,” Belasco said. “Women are bendier than men at pretty much every age, and it’s more common in people of African and Asian ancestry.”
Courseault’s research focuses on another potential contributor – the role of folate metabolism, or how the body processes folate (vitamin B9).
“We found a high prevalence of common MTHFR gene variants among patients with hypermobile Ehlers-Danlos syndrome and hypermobility spectrum disorders,” he explained. “These findings are preliminary and do not establish that MTHFR variants cause hypermobility, but they raise important questions about how metabolism and genetics may influence connective tissue biology.”
Of course, you can also increase your flexibility through consistent training, but that’s not quite the same thing as hypermobility.
“Dancers, gymnasts and swimmers can stretch their way into a lot more range in specific joints,” Belasco said. “That has a lot more to do with dynamic tendon and muscle strength and tone than joint capsule distensibility.”
Meanwhile, many people grow out of hypermobility in the transition from childhood to adulthood.
“Joint mobility generally decreases as we get older,” Courseault said. “However, losing flexibility doesn’t necessarily mean the underlying connective tissue dysfunction or associated symptoms disappear.”
And plenty of people with underlying genetic hypermobility still have unusually loose joints throughout their lives, which can lead to potential issues.
What are the downsides of hypermobility?
“While party-trick flexibility looks harmless, joint hypermobility creates chronic instability,” Brucato said. “In the foot and ankle, this makes people far more susceptible to recurrent ankle sprains because the stabilising ligaments can’t hold the joint firm on uneven ground.”
She added that hypermobile people are also more prone to severe plantar fasciitis, a condition that commonly causes pain on the bottom of the foot, especially in the heel.
“Because the arch over-stretches and collapses with every step, the plantar fascia is under constant, excessive tension,” Brucato said. “I have a patient who is a nurse with EDS who experienced such severe, chronic plantar fasciitis that conservative care failed, and she ultimately required surgery.”
Rafoth noted that the stretchy connective tissue in hypermobility or EDS “also overlaps significantly with skin problems such as sensitive skin, velvety skin, stretchy skin”.
For some people, hypermobility is harmless or even an advantage, but for others, the impact is more serious.
“Loose joints are less stable, so your muscles have to do more of the work holding things together,” Belasco said. “And your sense of where your joints are in space, called proprioception, isn’t always as sharp. That’s partly why we see more sprains, dislocations and overuse injuries – shoulders especially – in athletes.”
When the muscles need to work harder to compensate for lack of stability elsewhere, you may experience chronic pain, fatigue, altered movement, muscle tension and more.
“What I find particularly interesting is that many hypermobile patients actually complain of being extremely tight,” Courseault said. “This seems contradictory, but it makes sense when you understand the relationship between fascia, muscles and joint stability. You can have joints that are excessively mobile while the surrounding muscles and fascia feel incredibly tight.”
He added that some people with hypermobility also experience symptoms that involve multiple organ systems because connective tissue is found throughout the body. Two conditions he often sees in patients with symptomatic hypermobility are postural orthostatic tachycardia syndrome (POTS) – which can cause a rapid heart rate upon standing, dizziness, fatigue and exercise intolerance – and mast cell activation syndrome (MCAS), which can trigger flushing, itching, hives, gastrointestinal symptoms and other allergic-type reactions.
“I often compare hypermobility to owning a Ferrari,” Courseault said. “You have a body with unique performance characteristics and capabilities that can be advantageous, particularly in activities like dance, gymnastics and certain sports. But a Ferrari also requires specialised maintenance. If you don’t understand how to care for it, those same characteristics can become problematic.”
So how do you know when your hypermobility has crossed from a fun quirk into something worth getting checked out?
“If your flexibility is accompanied by chronic joint pain, frequent sprains, clicking or dislocations, it’s time to see a specialist,” Brucato said. “For hypermobile feet, standard supportive shoes aren’t always enough – custom orthotics are frequently required to physically block and limit that excessive motion before it causes long-term joint damage.”
Knowing the signs to pay attention to is an important first step.
“Patients should seek medical evaluation when their flexibility is accompanied by persistent pain, recurrent injuries, joint instability, unexplained fatigue, dizziness or symptoms affecting multiple body systems,” Courseault said. “These may be signs of a hypermobility spectrum disorder or hypermobile Ehlers-Danlos syndrome.”
He added that his practice focuses on identifying areas of dysfunction in the fascia and surrounding musculoskeletal system to reduce pain and improve stability and movement.
“Get checked if flexibility comes with pain lasting more than a few months, joints that slip out of place without a real injury, easy bruising, soft or stretchy skin, or things like fatigue, dizziness when you stand, or gut problems,” Belasco said.
“People wait 10 years or more on average for a diagnosis, so don’t shrug it off. The good news is that strength and balance training, done gradually, goes a long way.”
