EDUCATIONAL GUIDE
Leg Length Discrepancy: Causes, Symptoms & Treatment
A complete guide to understanding LLD — what causes it, how it’s diagnosed, and treatment options including custom shoe lift modifications.
~70%
Have Some LLD
3/8″+
Threshold to Treat
M21.7
ICD-10 Code
1/8″ – 6″
Lift Range
OVERVIEW
What Is Leg Length Discrepancy?
Leg length discrepancy (LLD) — also called leg length inequality or anisomelia — is a condition where one leg is shorter than the other. Classified medically under ICD-10 code M21.7. Up to 70% of people have some degree of LLD, but it typically only requires treatment when the difference exceeds 3/8 inch.
Two types exist: structural (actual bone-length difference) and functional (apparent difference from pelvic tilt or muscle imbalance). Both can cause back pain, hip pain, knee strain, and altered gait — but they’re treated differently. Always consult a physical therapist, orthopedic surgeon, or podiatrist for diagnosis.
CAUSES
Common Causes of LLD
LLD develops from many sources — congenital, traumatic, post-surgical, or progressive.
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Growth Differences
Bones grow faster or slower than the other leg during childhood — congenital or developmental.
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Fractures & Injuries
Improperly healed fractures or growth-plate injuries can permanently alter leg length.
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Medical Conditions
Polio sequelae, hemihypertrophy, cerebral palsy, juvenile arthritis, bone tumors.
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Functional Causes
Pelvic tilt, scoliosis, muscle imbalance, or hip joint contracture (no bone difference).
SYMPTOMS
Recognizing the Signs of LLD
Small differences (under 1/4″) often go unnoticed. Larger ones produce predictable patterns:
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Altered Gait / Limp
Visibly uneven walking pattern; fatigue from long distances; one foot strikes harder.
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Lower Back Pain
Chronic pain from pelvic tilt and uneven spinal load. Often the first symptom adults notice.
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Uneven Hips / Shoulders
One hip sits higher than the other; clothes hang asymmetrically.
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Knee & Hip Pain
Joint pain from compensatory loading. Can develop into early arthritis if untreated.
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Postural Issues
Functional scoliosis, head tilt, leaning to one side when standing.
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Uneven Shoe Wear
One shoe wears down faster than its pair. Asymmetric scuffing or heel cap erosion.
DIAGNOSIS
How LLD Is Diagnosed
Standing Block Test — boards under the shorter leg until hips appear level.
Tape Measurement — anatomical (ASIS to medial malleolus) length comparison.
X-Ray (Scanogram) — most accurate; measures bone length precisely.
CT or MRI — for complex cases involving prior surgery or growth plates.
If you have a measurement from your provider, use our guide to choose the correct lift height. If not, schedule a consultation first.
TREATMENT OPTIONS
Treatment Approaches
Most LLD cases are managed without surgery. Your provider determines the right path based on size of discrepancy, age, and underlying cause.
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Non-Surgical
Custom shoe lifts — most common treatment for discrepancies of 3/8″ to 4″. Bonded externally to the sole, fully reversible.
Heel inserts — for very small differences under 1/4″. Drop-in inserts that fit inside the shoe.
Physical therapy — addresses functional LLD through stretching, strengthening, and gait retraining.
Orthotics — for combined LLD and foot biomechanics issues. Best with podiatry consultation.
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Surgical
Limb lengthening — surgical bone-cutting (osteotomy) and gradual extension. Used for severe discrepancies, typically 2″+.
Epiphysiodesis — for growing children: surgically slows the longer leg’s growth plate so the shorter leg catches up.
Shortening procedures — removal of bone segments from the longer leg. Less common.
Joint replacement revision — for post-surgical LLD when a hip or knee replacement caused the discrepancy.
Consult an orthopedic surgeon for surgical evaluation.
OUR ROLE
How CNET Orthopedic Helps
We create custom shoe lift modifications that help patients regain balance, comfort, and confidence with every step.
Lift heights 1/8″ to 6″ — full clinical range.
Any shoe type — sneakers, boots, dress shoes, sandals, kids’.
Color-matched finishing — looks like factory work.
100% satisfaction guarantee — every modification.
STREAMLINED FITTING
Simple Mail-In Process
1. Submit an online order with shoe specs and lift height.
2. Receive a free shipping kit — prepaid USPS label, work form, box.
3. Mail us your shoes; we modify within 1–2 business days and ship back free.
Full details on our process page. Healthcare providers can arrange direct referral coordination.
FREQUENTLY ASKED
LLD Questions Answered
Can leg length discrepancy correct itself?
Structural LLD does not correct itself in adults. In growing children, mild cases sometimes equalize naturally. Functional LLD can often improve with physical therapy.
How much LLD requires treatment?
Most providers recommend treating discrepancies of 3/8 inch (about 1 cm) or greater. Smaller differences typically don’t cause symptoms.
Will untreated LLD cause long-term problems?
Untreated significant LLD (over 1/2″) can contribute to chronic lower back pain, hip and knee arthritis, scoliosis, and gait dysfunction. Earlier correction reduces risk.
Can children outgrow LLD?
Mild LLD in growing children may resolve. Significant differences usually require monitoring. Pediatric shoe lifts are common for ongoing correction.
Are external shoe lifts better than heel inserts?
For LLD over 3/8 inch, external lifts are preferred. Internal inserts crowd the shoe and cause heel slippage. External preserves cushioning and fit.
Will I need a doctor’s prescription?
No prescription required to order, but we strongly recommend consulting a PT, podiatrist, or orthopedic specialist to determine your correct lift height first.
Authoritative source: AAOS — Limb Length Discrepancy. This page is educational only — always consult a qualified healthcare provider.
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