Joint Laxity: Causes, Injury Risks, and Rehabilitation

Joint laxity refers to the degree to which a joint can move beyond what is considered a normal range, and it exists on a wide spectrum in the general population. Some people have one or two looser-than-average joints, while others have widespread flexibility that affects most joints in the body. Far from being a simple quirk of flexibility, laxity touches nearly every organ system built from connective tissue, and the science connecting loose joints to pain, injury risk, cardiovascular quirks, and even psychiatric conditions has expanded rapidly over the past decade.

What Makes Joints Loose at the Tissue Level

Ligaments and tendons are built from collagen fibrils bundled into fibers, and the way those fibrils are organized determines how stiff or stretchy a joint feels. When fibrils are tightly packed and aligned in parallel, a ligament resists stretching. When they are more scattered or fewer in number, the tissue gives way more easily. Research using computational models has confirmed that fibril alignment is a major driver of how a ligament behaves under load, and that disorganized fibrils produce measurably different stress responses than well-aligned ones.¹

One of the clearest windows into this comes from studies on collagen V, a regulatory protein that helps control how collagen fibrils assemble. Animal studies show that when collagen V is removed from tendons and ligaments, the fibrils grow larger in diameter but fewer in number, the tissue becomes less stiff, and the animal develops joint laxity and early-onset arthritis that closely mirrors what happens in classic Ehlers-Danlos syndrome.² The effect is not uniform across the body: the anterior cruciate ligament (ACL), which normally has a high collagen V content, loses more strength and stiffness than tendons elsewhere when collagen V is absent.³ That tissue-specific vulnerability helps explain why some joints are more dramatically affected than others in people with connective tissue disorders.

Who Has It and When It Changes

Joint laxity is extremely common in children and gradually decreases with age. A follow-up study of children found that the proportion meeting the highest hypermobility thresholds dropped from about a quarter to roughly six percent over two years, driven mainly by stiffening at the elbows and knees rather than the fingers.⁴ In childhood, boys and girls start out with similar flexibility scores, but puberty opens a gap. A study of young athletes found that before puberty, laxity scores were nearly identical between sexes, while after puberty, girls’ scores rose and boys’ scores did not.⁵

In adults, the sex gap widens further. Research on hypermobility features in men and women found that having two features of hypermobility was twice as common in women, having three features was four times as common, and having four features was eight times as common.⁶ Laxity declined with age in both sexes, but the timeline differed: men began losing flexibility in their mid-twenties, while women maintained their range through their mid-forties before a steeper decline set in.⁷

Hormones and the Moving Target of Ligament Stiffness

The sex difference in laxity is partly hormonal. A systematic review and meta-analysis of studies on sex hormones and ligament properties concluded that estradiol and relaxin have the strongest effects on both the mechanical and cellular behavior of ligaments in women.⁸ Relaxin, a hormone best known for loosening the pelvis in preparation for childbirth, affects connective tissue throughout the body. During pregnancy, fluctuations in estrogen, progesterone, and relaxin all contribute to increased laxity, altered collagen turnover, and ligament instability that can persist for months postpartum.⁹

This hormonal influence means that a woman’s joint stiffness is not a fixed number. It can shift across the menstrual cycle, ramp up during pregnancy, and change again at menopause. Athletes and their coaches have started paying attention to this, but practical guidelines for adjusting training around hormonal laxity changes are still in early stages.

How Laxity Is Measured

The standard clinical tool for assessing generalized joint hypermobility is the Beighton score, a set of nine maneuvers (bending the little finger back, touching the thumb to the forearm, hyperextending the elbows and knees, and touching the palms flat to the floor) that together produce a score from zero to nine. It is simple, quick, and widely used, but it has real limitations. Reliability studies generally produce moderate agreement between different examiners, with kappa values typically falling between 0.4 and 0.8.¹⁰ Intra-rater reliability (the same examiner measuring the same person twice) tends to be somewhat better, with one systematic review reporting correlations ranging from 0.74 to 0.99.¹¹

A practical problem is that the Beighton score only tests a handful of joints. You can have significant laxity in the shoulders, hips, or jaw and still score low. Individual joint measurements in degrees show even more variability between examiners, with agreement as low as 0.21 for some joints.¹² This means two clinicians could examine the same person and come away with meaningfully different impressions. If you’ve been told your joints are “normal” but you feel unstable, it may be worth getting a second opinion.

The Diagnostic Landscape

The terminology around laxity has shifted considerably. Before 2017, people with symptomatic hypermobility could receive overlapping diagnoses of joint hypermobility syndrome or Ehlers-Danlos syndrome, hypermobility type, depending on which criteria a clinician used. The 2017 international reclassification introduced a more structured framework: hypermobile Ehlers-Danlos syndrome (hEDS) was given stricter criteria, and a new umbrella term, hypermobility spectrum disorders (HSD), was created for people with symptomatic laxity who don’t meet the full hEDS criteria.¹³ The motivation was partly practical: two competing sets of criteria for what was essentially the same condition were confusing clinicians and patients alike.¹⁴

The distinction matters because hEDS and HSD are not just about flexible joints. Both can involve chronic pain, fatigue, and problems in systems well beyond the musculoskeletal. However, the 2017 criteria for hEDS remain controversial in some patient communities, partly because people who previously qualified now fall into the less-recognized HSD category. From a practical standpoint, the management approaches for both conditions overlap heavily.

Proprioception and the Sense of Where Your Body Is

A longstanding question is whether loose joints make it harder for the brain to sense joint position, a faculty called proprioception. The evidence is genuinely mixed. A recent study found that hypermobile adults made significantly larger errors when asked to replicate specific joint angles at both the elbow and knee compared to non-hypermobile adults, suggesting poorer proprioceptive accuracy.¹⁵ But a study of children found no proprioceptive differences between hypermobile and normally mobile kids.¹⁶

One way to reconcile these findings is that proprioceptive deficits may develop over time rather than being present from birth. Children’s nervous systems could be compensating effectively, while years of accumulated microtrauma and tissue stretching in adults gradually degrade the receptors embedded in ligaments and joint capsules. That is speculative, but the pattern of age-dependent differences shows up consistently enough to be worth investigating. Regardless of the mechanism, if you have lax joints and feel clumsy or off-balance, the proprioception angle is worth discussing with a physical therapist.

When Laxity Hurts

Many people with loose joints experience no pain at all, but a substantial subset develops chronic, widespread pain that can be difficult to manage. Research points to central sensitization as a key mechanism: the nervous system essentially turns up its pain volume in response to persistent low-level signals from unstable joints. Studies of people with hypermobile Ehlers-Danlos syndrome and joint hypermobility syndrome have found lowered thresholds for cold and heat pain and an increased wind-up response, which is when repeated stimuli produce escalating rather than steady pain signals.¹⁷ This pattern resembles what happens in fibromyalgia, and the two conditions may share an underlying pain mechanism.¹⁸

In adolescents, joint hypermobility has been correlated with central sensitization scores and heightened sensitivity of specific nerve fibers, and these changes tracked with greater functional disability.¹⁹ More recent work has linked this sensitized state in hEDS patients to a triad of fatigue, pain, and cardiac dysautonomia, suggesting the problem is systemic rather than confined to joints.²⁰ The clinical takeaway is that treating the pain in hypermobility requires addressing the nervous system’s amplified response, not just the joint itself.

Sports, Injury, and the ACL Problem

The relationship between laxity and sports injury is not as straightforward as “loose joints get hurt more.” A large survey of athletes found that sprains were actually more common among runners and other athletes who were not hypermobile.²¹ The thinking is that a joint with extra range of motion can absorb forces that would tear a stiffer joint. But that protective effect has clear limits. A meta-analysis of lower-limb injuries found that hypermobile athletes in contact sports had roughly a fivefold increased risk of knee injuries, with a combined odds ratio of 4.69.²² Ankle injuries, interestingly, showed no increased risk in the same analysis.

ACL injuries in particular deserve attention. There is consistent evidence that generalized joint hypermobility increases ACL injury risk, and when hypermobile patients do tear their ACL and undergo reconstruction, outcomes tend to be worse. One systematic review found that patellar tendon grafts performed better than hamstring tendon grafts in hypermobile patients, with less post-surgical laxity and better patient-reported outcomes.²³ If you have known hypermobility and are facing ACL surgery, raising this with your surgeon could influence graft selection.

Surgery and the Higher Failure Rate

Surgical outcomes in people with significant laxity tend to be less durable than in the general population, and ankle ligament repair is a case in point. A study comparing patients with Ehlers-Danlos syndrome or hypermobility spectrum disorders to matched controls found a 3.1-fold increase in revision surgery rates at five years after ankle ligament repair.²⁴ A separate study of the modified Broström procedure for chronic ankle instability found failure rates of about 11 percent in patients with generalized joint laxity versus under 2 percent in those without, along with lower functional scores and greater residual instability.²⁵

These numbers do not mean surgery is pointless for hypermobile patients, but they do mean that the risk-benefit calculation shifts. Exhausting conservative options first, choosing augmented surgical techniques when available, and setting realistic expectations about recovery timeline all become more important when the tissue you’re repairing is inherently stretchier than average.

Beyond the Joints

Connective tissue is everywhere, and laxity-related conditions can produce symptoms that seem unrelated to joints. One of the best-documented associations is with postural orthostatic tachycardia syndrome (POTS), a condition in which standing up triggers an abnormally fast heart rate. The working explanation is that lax connective tissue in blood vessel walls allows excessive blood pooling in the legs when upright, prompting a compensatory spike in heart rate and sometimes fainting.²⁶

Gastrointestinal symptoms are also common in people with hEDS, though the exact mechanisms are poorly understood. Connective tissue laxity in the gut wall, autonomic dysfunction affecting motility, medication side effects, and mental health comorbidities all likely contribute.²⁷ On the cardiovascular side, a study of people with hEDS and HSD found mitral valve prolapse in about 8 percent and some degree of aortic dilation in about 15 percent, though the dilation was mild in the vast majority of women and tended to be more significant in men.²⁸ A longitudinal study concluded that while aortic root size and valve issues were more common in patients with hypermobile and classic EDS, they were generally of little clinical consequence.²⁹

An underappreciated issue is that local anesthetics may wear off faster in people with hypermobile connective tissue. One proposed mechanism is that the anesthetic leaks away from the injection site more quickly through permeable connective tissue and into the bloodstream.³⁰ If dental numbing or local anesthesia has consistently failed for you, mentioning your joint flexibility to the provider is a worthwhile step.

The Neuropsychiatric Connection

One of the more surprising areas of laxity research is its overlap with psychiatric and neurodevelopmental conditions. A large case-control study found that adults with autism spectrum disorder were roughly three times as likely to meet criteria for generalized joint hypermobility as non-autistic adults, and nearly five times as likely when the hypermobility was symptomatic.³¹ A broader review found evidence linking joint hypermobility and hereditary connective tissue disorders to anxiety, depression, ADHD, developmental coordination disorder, eating disorders, and personality disorders.³²

The why remains unclear. One theory is that shared genetic pathways affect both connective tissue development and nervous system function. Another is that living with chronic pain, fatigue, and autonomic dysfunction creates the conditions for anxiety and mood disorders to develop over time. The association with autism, though, is harder to explain through a purely psychological pathway and hints at something more fundamental in development. None of this means that loose joints cause psychiatric conditions, but clinicians who see one should be alert for the other.

Exercise and Rehabilitation

Strengthening the muscles around loose joints is the most widely recommended non-surgical approach to managing laxity-related problems, and the logic is sound: if the passive restraints (ligaments) are too stretchy, the active restraints (muscles) have to pick up the slack. A randomized trial of spinal stabilization exercises in women with benign joint hypermobility syndrome found that the program reduced pain, improved trunk muscle endurance, and improved postural stability.³³

The picture becomes less clear with general resistance training. A randomized controlled trial of resistance training in women with generalized joint hypermobility found no significant differences between the exercise and control groups across multiple outcome measures, with high variability in individual responses.³⁴ That does not mean resistance training is useless for hypermobile people, but it does suggest that generic weight-room programs may need to be more carefully tailored. Exercises that emphasize joint control and stability under load, rather than raw strength, tend to be more relevant. The common advice to “just get stronger” is not wrong, but it undersells the specificity needed.

When Laxity Is an Advantage

Not all laxity is a problem. A study of over 600 musicians found that those with hypermobile wrists actually had lower rates of pain and stiffness in that region: about 5 percent reported symptoms compared with 18 percent of musicians without wrist hypermobility.³⁵ Hypermobile elbows showed a similar pattern, with symptoms in less than 1 percent versus 2 percent of those with normal elbows. The flexibility apparently allowed the joints to handle the repetitive demands of playing an instrument with less strain. The story was different at the spine and knees, where hypermobile musicians had more symptoms than their stiffer peers.³⁶ The pattern fits with what we know about tissue-specific effects: small joints under controlled, repetitive motion may benefit from extra range, while weight-bearing or axially loaded structures pay a price for it.

Dance, gymnastics, and certain martial arts have long selected for flexibility, and many successful performers have some degree of generalized laxity. The key distinction is between someone whose nervous system has learned to control that range and someone whose muscles and reflexes cannot keep up with it. Laxity with excellent neuromuscular control is an asset. Laxity without it is a vulnerability.