“Double jointed” is a common but misleading term. Nobody actually has extra joints. What the phrase describes is joint hypermobility, a condition in which one or more joints move beyond the range that most people consider normal. The underlying cause involves the connective tissue that holds joints together, and depending on how widespread and symptomatic it is, hypermobility can range from a benign party trick to a complex medical condition with effects that reach well beyond the joints themselves.
No Extra Joints, Just Looser Ones
The name “double jointed” suggests some kind of structural bonus, as if the person were built with spare hinges. In reality, every hypermobile person has the same number of joints as everyone else. The difference is in what surrounds and stabilizes those joints. Connective tissue proteins, especially collagen, provide the tensile strength in tendons, ligaments, and joint capsules. When genetic variations alter how those proteins are produced or assembled, the tissues become stretchier than usual, and joints gain a wider range of motion.
Research into collagen’s role has shown this directly. Animal studies in which collagen V was selectively deleted from tendons and ligaments produced joint laxity strikingly similar to what’s seen in hypermobile humans, along with altered mechanical properties in key stabilizing structures like the anterior cruciate ligament.1The American Journal of Pathology. Targeted Deletion of Collagen V in Tendons and Ligaments Results in a Classic Ehlers-Danlos Syndrome Joint Phenotype A broader review of membrane proteins involved in joint hypermobility syndrome concluded that the cause is likely rooted in genetic changes affecting proteins that add flexibility and strength to joints, ligaments, and tendons, with collagen being a primary suspect.2PubMed Central. Joint Hypermobility Syndrome and Membrane Proteins: A Comprehensive Review Despite these leads, the full genetic picture remains incomplete. Only a handful of genetic markers linked to joint laxity and flexibility have been identified so far, and the genetic basis of non-syndromic hypermobility is still largely unknown.3ScienceDirect. Genetics of flexibility
How Common Is Hypermobility
Joint hypermobility is far more common than most people assume, especially in young people. A meta-analysis pooling data from twenty studies found that about a third of children and adolescents met criteria for joint hypermobility. Girls were roughly twice as likely to be hypermobile as boys, with a prevalence of about 33% in girls compared to 18% in boys.4PubMed Central. Prevalence of joint hypermobility in children and adolescents: A systematic review and meta-analysis Another systematic review found prevalence in children varied widely across countries and ethnic groups, ranging from roughly 9% to 36% depending on the population studied and the scoring threshold used.5PubMed Central. Hypermobility prevalence, measurements, and outcomes in childhood, adolescence, and emerging adulthood: a systematic review
Hypermobility tends to decrease with age. Many children who are bendy at ten will notice their joints stiffening through adolescence and into adulthood. The sex difference, though, persists throughout life. Hormonal factors appear to play a role: fluctuating sex hormone levels in young women and the loss of ovarian hormone production after menopause influence connective tissue behavior and contribute to observed differences in joint function between men and women.6PubMed Central. Hormonal modulation of connective tissue homeostasis and sex differences in risk for osteoarthritis of the knee Ethnicity matters too: people of Asian and African descent generally show higher rates of joint hypermobility than people of European descent, though the reasons for this are not well understood.
How Doctors Test for It
The standard clinical tool is called the Beighton Score. It checks nine specific movements: bending each pinky finger backward past 90 degrees, pressing each thumb to the forearm, hyperextending each elbow and each knee, and placing the palms flat on the floor with straight legs. Each successful maneuver earns a point, and the total ranges from zero to nine. For adults, a score of five or higher is generally considered the threshold for generalized joint hypermobility, while children need a score of at least six because they are naturally more flexible.7PubMed. Measurement properties of clinical assessment methods for classifying generalized joint hypermobility-A systematic review
The Beighton Score is widely used and has reasonable reliability between different examiners, but it has real limitations. A systematic review found that while the score’s consistency between raters was decent, its actual validity is harder to confirm because of methodological problems in the studies that have tested it.8bioRxiv. A Systematic Review of the Beighton Score Compared with Other Commonly Used Measurement Tools for Assessment and Identification of Generalised Joint Hypermobility (GJH) One key issue is that the score only tests a handful of joints, so someone with significant hypermobility in their shoulders or hips but not their fingers could score below the threshold. Clinicians are increasingly advised to combine the Beighton Score with a patient’s history of past flexibility, since joints often stiffen with age and someone who was clearly hypermobile at twenty may not meet the cut-point at fifty.
When Flexibility Becomes a Medical Problem
Having a high Beighton Score doesn’t automatically mean something is wrong. Plenty of hypermobile people go through life with nothing more than the ability to do unsettling things at parties. The medical concern starts when hypermobility comes with symptoms, and the terminology has gotten more precise in recent years. In 2017, an international classification replaced older catchall terms with two main categories: hypermobile Ehlers-Danlos syndrome (hEDS) for people who meet a strict set of diagnostic criteria, and hypermobility spectrum disorders (HSD) for people with symptomatic hypermobility who don’t quite meet that bar.9PubMed. Hypermobile Ehlers-Danlos Syndrome and Hypermobility Spectrum Disorders
This distinction sounds tidy on paper, but the clinical reality is murkier. A study comparing patients diagnosed with hEDS to those diagnosed with HSD found that the two groups showed very similar disease severity and the same spectrum of extra-articular problems. The hEDS group had somewhat worse pain, motor difficulties, and bleeding, but bone fragility, nerve pain, and mast cell issues were equally common in both groups. The authors suggested treating hEDS and HSD as a single entity requiring the same approach.10PubMed Central. Are patients with hypermobile Ehlers-Danlos syndrome or hypermobility spectrum disorder so different? This is worth knowing if you’ve been told you “only” have HSD, as your symptoms may still warrant the same attention.
Pain and the Problem With Proprioception
Of all the complications that come with symptomatic hypermobility, chronic pain is the most common and often the hardest to manage. While extra flexibility can genuinely help with mobility and agility, the flip side of lax and fragile tissue is a body that struggles to stabilize itself, leading to repeated microinjuries, muscle fatigue from overcompensation, and pain that can spread well beyond any single joint.11PubMed. Joint hypermobility syndrome pain
Hypermobile people also tend to have worse proprioception, which is your body’s sense of where your limbs are in space without looking at them. Research has found that hypermobile individuals make significantly larger errors when asked to reproduce specific joint angles with their elbows and knees, suggesting their internal body-position sense is less accurate than in non-hypermobile people.12PubMed Central. The effects of joint hypermobility on strength, proprioception, and functional performance Similar proprioceptive impairment has been demonstrated specifically in people with hypermobile Ehlers-Danlos syndrome, who showed significantly worse knee joint repositioning compared to controls.13PubMed. Joint position sense and vibratory perception sense in patients with Ehlers-Danlos syndrome type III (hypermobility type)
This isn’t just a laboratory curiosity. Poor proprioception contributes to the clumsiness and frequent falls that many hypermobile people report. It also helps explain why hypermobile joints are prone to injury: if your nervous system is slightly less accurate about where your joint is at any given moment, the muscles responsible for stabilizing it are always a beat behind.
Beyond the Joints
One of the most surprising aspects of hypermobility, and one that patients often struggle to get taken seriously, is how far the effects can reach beyond the musculoskeletal system. The connective tissue that makes joints flexible is the same stuff found throughout the body, including in blood vessel walls, the gut, the skin, and the nervous system. When that tissue is structurally different, multiple organ systems can be affected.
A growing body of research has identified a cluster of conditions that frequently travel together: hypermobility spectrum disorders or hEDS, postural orthostatic tachycardia syndrome (POTS, a form of dysfunction in the autonomic nervous system that controls heart rate and blood pressure), and mast cell activation syndrome (MCAS, which involves overactive immune cells). People with this cluster frequently report significant and sometimes disabling gastrointestinal symptoms.14PubMed Central. The Suggested Relationships Between Common GI Symptoms and Joint Hypermobility, POTS, and MCAS The GI problems are thought to stem in part from autonomic dysfunction: the nervous system that normally keeps digestion running smoothly doesn’t regulate gut activity properly, leading to symptoms like nausea, bloating, reflux, and constipation.15Frontiers in Neurology. An overview of Ehlers Danlos syndrome and the link between postural orthostatic tachycardia syndrome and gastrointestinal symptoms with a focus on gastroparesis
A study looking specifically at people with HSD or hEDS who also had POTS found that these individuals were significantly more likely to meet criteria for functional gastrointestinal disorders across multiple organ domains, and that association held even after accounting for other common overlapping conditions like chronic fatigue syndrome and fibromyalgia.16PubMed. Functional gastrointestinal disorders are increased in joint hypermobility-related disorders with concomitant postural orthostatic tachycardia syndrome If you’re hypermobile and also dealing with unexplained gut problems, dizziness on standing, or feeling faint, these symptoms may be connected rather than coincidental.
The Neurodivergence Link
One of the more intriguing recent findings is the association between joint hypermobility and neurodivergent conditions like autism and ADHD. A study comparing neurodivergent individuals to the general population found that about half of the neurodivergent group met criteria for hypermobility, with odds of hypermobility more than four times higher than the general population rate. The number of hypermobile joints also mediated the relationship between neurodivergence and symptoms of both autonomic dysfunction and pain, meaning the more hypermobile joints someone had, the more these other symptoms tracked with their neurodivergent status.17PubMed Central. Joint Hypermobility Links Neurodivergence to Dysautonomia and Pain
A separate study of hypermobile individuals with anxiety found that almost half scored above clinical thresholds for likely autism, and about a fifth scored above the threshold for likely ADHD. The number of connective tissue features a person had correlated positively with sensory sensitivities, autistic characteristics, ADHD characteristics, and autonomic hyperactivity.18npj Mental Health Research. Beyond bendy joints: number of variant connective tissue features predicts neurodivergent characteristics in hypermobile individuals with anxiety The mechanism behind this overlap isn’t settled, but it may involve shared neurodevelopmental pathways or the fact that connective tissue differences affect the nervous system as well as the joints. For now, these associations are consistent enough that clinicians working with hypermobile patients are increasingly screening for neurodivergent traits, and vice versa.
Exercise and Managing Symptomatic Hypermobility
If you’re hypermobile and dealing with pain or instability, the evidence consistently points toward exercise as the primary management tool, though the specifics are less clear than you might hope. A systematic review of therapeutic exercise for joint hypermobility syndrome found that people who exercised improved over time in pain, quality of life, strength, proprioception, and balance, with no reported adverse effects. However, the review could not show that any one type of exercise was clearly superior to another: generalized exercise wasn’t convincingly better than joint-specific work, and targeted knee exercises didn’t outperform a control condition.19Physiotherapy. The effectiveness of therapeutic exercise for joint hypermobility syndrome: a systematic review
A randomized controlled trial of resistance training in women with generalized joint hypermobility found no significant differences between the training group and controls across any outcome measure, with high variability between participants.20PubMed Central. Effect of resistance training on muscle properties and function in women with generalized joint hypermobility: a single-blind pragmatic randomized controlled trial That doesn’t mean resistance training is useless; it may mean that hypermobile people respond very differently from one another, and that a standard program doesn’t work for everyone the same way. Physiotherapists who specialize in hypermobility often emphasize controlled, progressive strengthening and proprioceptive training rather than stretching, which most hypermobile people already have far too much of.
Pregnancy and Hormonal Shifts
Pregnancy is a time when hypermobility can become noticeably more problematic. The hormone relaxin, which prepares the pelvis for childbirth by loosening connective tissues, peaks during the first trimester.21PubMed Central. Generalized joint hypermobility and the risk of pregnancy-related pelvic girdle pain: Is body mass index of importance? In someone whose connective tissue is already stretchier than usual, this hormonal surge can push joint laxity past the point of comfortable function. More broadly, the hormonal changes of pregnancy, involving estrogen, progesterone, and relaxin together, alter collagen dynamics and ligament stability, predisposing pregnant people to low back pain, pelvic girdle pain, and other musculoskeletal problems.22PubMed Central. Neuromusculoskeletal disorders in pregnancy revisited: Insights and clinical implications
For women who are already hypermobile, the combination of pre-existing tissue laxity and pregnancy hormones can be particularly challenging. Research suggests that women with generalized joint hypermobility and a higher body mass index face elevated odds of pelvic girdle pain in early pregnancy, possibly because the elastic tissue responds more strongly to the rapid hormonal increase when combined with the mechanical stress of extra weight.21PubMed Central. Generalized joint hypermobility and the risk of pregnancy-related pelvic girdle pain: Is body mass index of importance? Knowing you’re hypermobile before becoming pregnant can help you and your care team plan for the musculoskeletal challenges that pregnancy is likely to amplify.
Why Local Anesthesia Sometimes Doesn’t Work
One of the stranger and more practically frustrating aspects of connective tissue disorders is that local anesthesia frequently fails or works poorly. In a large survey of people with Ehlers-Danlos syndromes who had undergone dental procedures, 88% recalled inadequate pain prevention from local anesthetic, compared to only 33% of respondents without EDS.23PubMed Central. Resistance to local anesthesia in people with the Ehlers-Danlos Syndromes presenting for dental surgery That’s a dramatic difference, and it’s consistent with what patients have been reporting for decades.
The intuitive explanation would be that the anesthetic disperses too quickly through loose connective tissue, but research has tested that hypothesis and found it doesn’t hold up: a study using radiolabeled solution showed that dispersal rates in EDS tissue were not significantly different from normal tissue.24British Journal of Plastic Surgery. Dispersal of radioisotope labelled solution following deep dermal injection in Ehlers-Danlos syndrome The actual mechanism remains unknown. Some researchers suspect differences in sodium channel function or nerve membrane properties, but this hasn’t been pinned down. Regardless of the why, the practical takeaway is real: if you have hypermobile EDS or a related condition, telling your dentist or surgeon in advance can help them adjust their approach, whether through higher doses, different anesthetic agents, or simply extra time to let the anesthetic take effect.
How the Same Trait Looks Different in Athletes
Not everyone with hypermobile joints ends up in a rheumatologist’s office. In fields like dance, gymnastics, and certain martial arts, extra range of motion is actively selected for and can be a genuine competitive advantage. Dancers with hypermobile spines and hips can achieve lines that stiffer-bodied performers cannot. Gymnasts with hypermobile shoulders can reach positions that would be impossible otherwise.
But the same tissue laxity that enables those feats also raises injury risk, and this creates a genuine tension that athletes in these fields have to manage throughout their careers. Young female athletes in particular experience a higher incidence of ligament injuries than their male counterparts, and hypermobility is a recognized risk factor for osteoarthritis development.6PubMed Central. Hormonal modulation of connective tissue homeostasis and sex differences in risk for osteoarthritis of the knee A hypermobile dancer may perform beautifully for years and then face joint problems in their thirties that their less flexible peers avoid. The trait isn’t cleanly good or bad; it’s a trade-off, and how it plays out depends enormously on what you do with your body, how strong the muscles around your joints are, and whether the hypermobility is localized or generalized.
This is part of why the blanket term “double jointed” is so misleading. It implies a single thing, when in reality it describes a wide spectrum. At one end, you have a teenager who can bend their thumb backward and occasionally impress friends. At the other, you have someone managing chronic pain, digestive problems, fainting episodes, and anesthesia failures, all rooted in the same underlying connective tissue variation. Understanding which end of the spectrum you fall on, and that it even is a spectrum, is the first step toward knowing whether your hypermobility is a quirk or a condition that deserves medical attention.