Both hips can develop pain when one leg is shorter than the other, but the shorter leg’s hip tends to take the brunt of it. A large combined analysis of over 3,000 participants found that the hip on the shorter side had roughly 1.5 times the odds of developing radiographic osteoarthritis compared to matched controls, while the longer leg’s hip showed no statistically significant increase in risk. The picture is more complicated than “short side hurts, long side doesn’t,” though, because the type of pain, the size of the discrepancy, and whether you’re standing, walking, or running all shift which hip bears more strain.
How a Leg Length Difference Changes the Way Your Hips Work
When one leg is even slightly shorter than the other, your pelvis tilts to compensate. The short side drops, and the long side rises. Research simulating different magnitudes of leg length discrepancy showed that pelvic tilt and torsion increased as the discrepancy grew, even when spinal posture stayed essentially the same.1PubMed Central. The effect of simulating a leg-length discrepancy on pelvic position and spinal posture That pelvic drop means the short leg’s hip joint has to work harder just to keep you upright. Specifically, the abduction moment at the short-side hip increases significantly, meaning the muscles on the outer side of that hip are pulling harder during every step.2PubMed Central. Hip joint load in relation to leg length discrepancy
On the long-leg side, the body tries a different set of tricks. A study of children with mild discrepancies found that the long leg’s joints adapt to functionally shorten it, with the clearest compensations appearing in the group with a 2 to 3 centimeter difference.3PubMed. Impact of mild leg length discrepancy on pelvic alignment and gait compensation in children The long-side hip tends to flex more and adduct more during mid-stance, essentially tucking itself in to avoid swinging outward. These compensatory patterns don’t always reach statistical significance in controlled lab conditions, but they accumulate over thousands of daily steps.4Journal of Korean Physical Therapy. Leg Length Discrepancy to Influence on Kinematic Changes of the Pelvis and the Hip during Gait
Which Hip Develops Osteoarthritis
The strongest evidence on this question comes from a combined analysis of two large osteoarthritis cohort studies. For people with a leg length difference of at least 1 centimeter, the odds of existing radiographic hip osteoarthritis were about 47 percent higher on the shorter leg compared to controls, while the longer leg showed no meaningful increase. When the discrepancy reached 2 centimeters or more, the risk jumped substantially: people with that level of inequality had over four times the odds of developing new hip osteoarthritis in the shorter leg over follow-up, while the longer leg again showed no significant elevation.5PubMed Central. Leg Length Inequality and Hip Osteoarthritis in the Multicenter Osteoarthritis Study and the Osteoarthritis Initiative
This finding may seem counterintuitive. The shorter leg bears less body weight during standing, so why would its hip wear out faster? The answer lies in those altered loading patterns. The short-side hip doesn’t just carry weight straight down; it deals with increased lateral forces, increased rotational strain, and a pelvis that tilts away from it. Cartilage that absorbs load at an angle wears differently from cartilage loaded squarely, and over years this uneven distribution appears to accelerate joint breakdown.
An older, smaller clinical study of 36 patients with hip osteoarthritis found the opposite pattern: most of the diseased hips were on the side of the longer leg. The authors argued that when you account for the shortening caused by the disease itself (as cartilage erodes and the femoral head collapses, the affected leg gets shorter), many of those “long legs” were actually the longer leg before disease set in.6PubMed Central. Studies in osteoarthritis of the hip. II. Osteoarthritis of the hip and leg-length disparity A 29-year follow-up study added another wrinkle: among patients who eventually needed hip or knee replacement surgery, arthroplasty was performed on the longer leg about three times as often as the shorter leg.7PubMed Central. Is a long leg a risk for hip or knee osteoarthritis? A 29-year follow-up study of 193 individuals The discrepancy between these studies and the larger cohort analysis is real, and researchers haven’t fully resolved it. The safest summary is that both hips are at increased risk compared to someone with legs of equal length, but the shorter leg appears to face the higher risk of radiographic osteoarthritis based on the largest available data.
Lateral Hip Pain and Trochanteric Bursitis
Osteoarthritis isn’t the only source of hip pain. Many people with a leg length difference experience pain on the outside of the hip, over the bony prominence called the greater trochanter. This area is where the gluteus medius and minimus tendons attach, and it’s home to a fluid-filled sac that can become inflamed. Leg length inequality has been specifically associated with greater trochanteric bursitis, alongside low back pain and degenerative hip disease.8Elsevier / ScienceDirect. Rheumatic disease aspects of leg length inequality
This type of pain tends to show up on the short-leg side, for the same biomechanical reason driving the increased abduction moment. The muscles on the outer hip of the shorter leg are working overtime with every stride to stabilize a pelvis that’s tilting away from them. Over time that repeated strain irritates the tendons and the bursa beneath them. If you’ve been told you have “hip bursitis” or “greater trochanteric pain syndrome” and also have a leg length difference, the two are likely connected.
How Big Does the Difference Need to Be
Most adults have some small asymmetry between their leg lengths. A difference of a few millimeters is nearly universal and doesn’t cause problems. The threshold where symptoms typically start appearing is somewhere around 1 to 2 centimeters. In the large cohort study mentioned earlier, statistically meaningful increases in hip osteoarthritis risk appeared at the 1-centimeter mark, with dramatic jumps at 2 centimeters.5PubMed Central. Leg Length Inequality and Hip Osteoarthritis in the Multicenter Osteoarthritis Study and the Osteoarthritis Initiative A separate cohort of over 3,000 participants included 206 individuals with a discrepancy of 2 centimeters or more, giving some indication of how common the larger differences are.9PubMed Central. Symptoms of the knee and hip in individuals with and without limb length inequality
A narrative review of the spinal implications pegged the threshold at roughly 20 millimeters (2 centimeters) for significant biomechanical alteration and functional scoliosis.10PubMed Central. Overview and Spinal Implications of Leg Length Discrepancy: Narrative Review But individual variation is huge. Some people tolerate a 1.5-centimeter difference without any symptoms, while others develop pain at smaller discrepancies, especially if they’re runners or spend long hours on their feet. Your body’s ability to compensate depends on muscle strength, joint flexibility, and how much repetitive loading you put through your legs.
Structural Versus Functional Leg Length Differences
Not every apparent leg length difference means one bone is actually shorter. There are two categories, and distinguishing between them changes the treatment entirely. A structural discrepancy means the bones themselves differ in length, whether from a fracture, a growth plate issue in childhood, or a congenital condition. A functional discrepancy means the bones are the same length but something in the pelvis, spine, or foot makes one leg behave as if it’s shorter. Causes include a tight hip flexor that tilts the pelvis, flat feet on one side that drops the ankle, or a joint contracture that prevents full extension.
The treatment diverges sharply. Structural asymmetries are typically addressed with a heel lift, usually starting at about half the measured difference. Functional asymmetries are treated by correcting the underlying cause, often with orthotic inserts, targeted stretching, or manual therapy.11Clinics in Podiatric Medicine and Surgery. Functional and Structural Limb Length Discrepancies: Evaluation and Treatment If you slap a heel lift under a foot when the problem is actually a pelvic rotation, you can make things worse. Getting the diagnosis right matters more than the treatment choice.
How Leg Length Differences Are Measured
Your clinician might start with a tape measure from the pelvis to the ankle bone, or have you stand on blocks of different heights under the shorter leg until your pelvis looks level. These clinical methods are useful as screening tools but aren’t especially precise. Imaging is more accurate, and a full-length standing X-ray provides the most comprehensive picture with relatively low radiation exposure.12PubMed Central. Methods for assessing leg length discrepancy CT scans and biplanar radiography systems produce measurements that closely agree with each other, generally within a few millimeters.13PubMed. Assessment of lower limb length and alignment by biplanar linear radiography: comparison with supine CT and upright full-length radiography For most clinical decisions, the standing X-ray hits the sweet spot of accuracy, cost, and radiation dose.
What Happens Above the Hip
A leg length difference doesn’t stop at the pelvis. The tilted pelvis forces the spine to compensate, and one common result is a functional scoliosis, a lateral curve that appears when standing and partially or fully corrects when the discrepancy is eliminated (for instance, by standing on a lift).14PubMed Central. Scoliosis and Lower Limb Inequality: To Lift or Not to Lift, That Is the Question Unlike structural scoliosis, which involves a permanent change in vertebral shape, this type is driven entirely by the pelvic tilt and can be reversed by addressing the leg length issue. But if the discrepancy persists for years, the spine can develop permanent degenerative changes in the facet joints and discs.10PubMed Central. Overview and Spinal Implications of Leg Length Discrepancy: Narrative Review Low back pain is probably the most frequently reported symptom in people with a meaningful leg length difference, and it often coexists with hip pain on the short side.
The Sensation of Unequal Legs When There Isn’t One
Here’s a twist that catches a lot of people off guard: pain itself can create the feeling that your legs are different lengths, even when they’re not. People with low back pain, sciatica, or hip osteoarthritis often report sensing that one leg is shorter. One proposed explanation is neurological. When there’s pressure on sensory nerves, particularly the dorsal spinal roots, it can cause an increased signal from muscle spindle fibers, which are the sensors inside your muscles that report on length and stretch. The result is a perceived change in leg length that’s neurophysiological, not anatomical. This creates a confusing chicken-and-egg problem: does the leg length difference cause the pain, or does the pain create the sensation of a leg length difference? In many cases, the answer is probably both, operating in a feedback loop.
When Hip Pain Appears After Hip Replacement Surgery
Leg length discrepancy is one of the most common complaints after total hip replacement, and it’s a leading cause of patient dissatisfaction and legal disputes in orthopedic surgery.15PubMed Central. Leg length discrepancy after total hip arthroplasty: a review of literature The artificial joint can be positioned in a way that makes the operated leg slightly longer or shorter than the other side. Here the pattern flips from what we see with natural discrepancies. After hip replacement, a leg that ends up longer than the other side tends to cause more pain than one that ends up shorter. Patients with a shorter operated leg are more prone to limping, but patients whose operated leg came out longer report more pain.16PubMed. Influence of leg length discrepancy on clinical results after total hip arthroplasty–a prospective clinical trial A review of the literature confirmed this pattern: where postoperative leg length inequality exists, lengthening appears to cause more problems than shortening.17PubMed. A review of symptomatic leg length inequality following total hip arthroplasty
Why would a surgically lengthened leg hurt more? The muscles, tendons, and nerves around the hip are suddenly being stretched beyond their accustomed length. The iliotibial band, the sciatic nerve, and the hip abductors are all on tension, and the body has no time to gradually adapt the way it might with a discrepancy that develops slowly over years. If you’ve had a hip replacement and notice that the operated side feels “too long” or that your pain is more on that side, this is worth discussing with your surgeon, as it’s a well-recognized and sometimes correctable issue.
Heel Lifts and Shoe Modifications
For people whose leg length difference is structural and causing symptoms, the simplest intervention is a heel lift or shoe modification on the shorter side. A systematic review found that across available studies, roughly 88 percent of patients treated with a shoe lift experienced partial or complete pain relief.18PubMed. Shoe Lifts for Leg Length Discrepancy in Adults With Common Painful Musculoskeletal Conditions: A Systematic Review of the Literature That sounds impressive, but the evidence quality was rated as low, meaning the studies had design limitations that make it hard to be confident in the exact number. A separate systematic review of foot orthoses and footwear interventions for people with hip pain found moderate improvement in pain, again with very low to low certainty of evidence.19PubMed. Effects of foot orthoses and footwear interventions on impairments and quality of life in people with hip pain: A systematic review
The practical advice from clinicians is to start conservatively. A lift that corrects about half the measured discrepancy is standard initial practice, because going straight to full correction can overload the opposite side or create new problems. Some people do best with an in-shoe insert for differences under about 1 centimeter, switching to an external shoe modification for larger corrections. Bilateral motion-control shoes with sole adjustments have been shown to reduce vertical ground reaction forces on the short side during walking, which is a measurable way of confirming that the intervention is actually offloading the affected hip.20Gait & Posture. Impact of bilateral motion control shoes with outsole adjustment on gait asymmetry in individuals with mild leg length discrepancy
Athletes and Repetitive Loading
The stakes go up considerably for runners and other athletes who put thousands of repetitive impacts through their legs. A clinical survey of over 4,000 athletes and long-distance runners found that nearly 40 percent had some form of limb length discrepancy. Among those athletes, there was a high correlation between injuries and the short-leg side, along with associated weakness on that side.21Journal of Orthopaedic & Sports Physical Therapy. Limb length discrepancies of the lower extremity (the short leg syndrome) Many of these discrepancies were functional rather than structural, involving overpronation of one foot or pelvic imbalances that created the effective shortening. For a runner logging high weekly mileage, even a difference too small to cause symptoms during daily walking can produce overuse injuries over time. Stress fractures, iliotibial band syndrome, and hip flexor strains tend to cluster on the side dealing with the greater biomechanical compromise, which in athletes is frequently the short-leg side.
If you’re a runner dealing with recurring one-sided hip or leg pain that doesn’t respond to the usual rest-and-rehab approach, it’s worth having your leg lengths checked. A functional difference from foot mechanics or pelvic alignment can sometimes be corrected with an orthotic that eliminates the asymmetry, while a structural difference may need a shoe modification. The fix doesn’t have to be complicated, but it does need to start with identifying which type of discrepancy you have.