Most of us assume that our legs are the same length — after all, why wouldn’t they be? But in reality, many people (over 75%) have a small difference in leg length, and for some, it’s more than just a curious anatomical quirk. A study published in Archives of Physical Medicine and Rehabilitation in 2005 investigated whether very mild leg-length discrepancies — less than 1 cm — could contribute to chronic low back pain and whether simple corrective measures might help.
What Is Leg-Length Discrepancy?
Leg-length discrepancy (LLD) refers to a condition in which one leg is anatomically longer than the other. This can be due to a variety of causes — congenital differences in bone growth, injuries that affect a growth plate, or even surgical history. While large discrepancies often lead to obvious gait disturbance and are treated surgically, smaller differences are subtle and sometimes dismissed as clinically insignificant.
But even small discrepancies can influence the musculoskeletal system, particularly when it comes to posture, gait, and low back mechanics. After all, if your legs push up from the ground at slightly different heights, your pelvis may tilt, your spine might adjust its curvature, and muscles on one side of the body may have to work harder to keep you balanced.
The 2005 Study: Can Small Lifts Help Reduce Back Pain?
The 2005 clinical trial examined whether conservative correction — specifically shoe lifts designed to correct leg-length differences of 10 mm or less — could help relieve chronic low back pain. This is notable because most clinical practice tends to focus on larger discrepancies (2 cm or more) before intervening.
Here’s what the study found:
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Even mild discrepancies (as little as 10 mm) can contribute to changes in biomechanics during standing and walking.
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When such discrepancies were corrected with shoe lifts, there were measurable improvements in symptoms for people with chronic low back pain.
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This suggests that even very subtle differences in leg length may be functionally important — especially when the body’s alignment and compensatory muscular demands are considered.
Importantly, the trial wasn’t about major orthopedic intervention; it was about whether something as simple as a small lift inside your shoe could make a meaningful difference in how your body feels and functions. This is a powerful idea because it means that everyday adaptations might help some people avoid more invasive treatments.
Why Even Small Discrepancies Matter
A leg-length difference doesn’t have to be dramatic to have meaningful effects. Other research has shown that:
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LLD can influence pelvic alignment, leading to pelvic tilt and compensatory changes in the spine and gait pattern.
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Pelvic tilt and spinal curvature changes may contribute to discomfort, muscular imbalance, and asymmetric loading of joints, which over time can exacerbate pain or lead to overuse injuries.
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As little as 5 mm of difference has been linked, in some studies, to increased risk of long-term musculoskeletal issues, including hip and knee pathology.
These effects don’t happen in isolation. The human musculoskeletal system is integrated from head to toe: a tilt in the pelvis can influence the lower back, which in turn can affect how the shoulders and neck align. So even a subtle change at the feet can theoretically ripple upward through the body’s alignment.
Understanding Gait and Compensation
When one leg is slightly longer than the other, the body adapts. Instead of simply ignoring the difference, the neuromusculoskeletal system makes adjustments — sometimes in unexpected ways:
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The pelvis tilts to compensate for the height difference.
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Muscles on one side of the body work harder to maintain a level head and trunk.
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Gait patterns subtly shift, which over time may contribute to asymmetries in movement and muscle fatigue.
These changes may not always be noticeable to the naked eye. In fact, most people with mild LLD don’t limp, but still show functional adaptations during walking or standing that could lead to discomfort. Biomechanical analysis often reveals asymmetries in joint angles and muscle activation even when surface observation seems normal.
Practical Takeaways
What does this mean for someone reading at home?
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Small differences can still matter. Even a leg-length discrepancy of less than a centimeter isn’t necessarily trivial — especially if you have unexplained low back pain or asymmetrical muscle tightness.
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Diagnostic evaluation helps. Only a specialist trained in these evaluations should perform measurements — to determine whether LLD might be contributing to symptoms. If you doctor or therapist does not take an X-ray to evaluate this they do not know what they are doing. The literature is EMPHATIC that x-ray is the gold standard of evaluation.
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Simple adjustments may help. Conservative measures like shoe lifts or custom orthotics are low-risk options that, in some cases, have been shown to reduce pain and improve comfort.
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It’s not just about leg length. Body mechanics, posture, activity level, and muscular strength all play roles in how LLD affects you. Correcting alignment is only one piece of a comprehensive approach.
Final Thought
Leg-length discrepancies are more common than most people realize, and they often go unnoticed because the body initially adapts. However, research suggests that even mild differences — once thought too small to matter — can affect biomechanics and contribute to symptoms like low back pain. This growing body of evidence supports the idea that careful assessment and individualized interventions — even simple ones like shoe lifts — deserve consideration in the management of chronic musculoskeletal discomfort. At Charles Street Family Chiropractic, we have been helping people have a better life without pain though managing leg length imbalances for 36 years. For more information you can access our blog articles and reserach tab at our Boston Chiropractic office. Call us today at 617-720-1992 to see if we can help you lead a better life.