Leg length discrepancy (LLD) is a condition in which one leg is measurably shorter than the other. It is more common than most people realise — a clinically significant discrepancy is present in a substantial proportion of the population, yet it frequently goes undiagnosed as a contributing factor in chronic lower limb and back pain.
There are two distinct types, which require different management approaches. True LLD involves an actual difference in bone length — in the femur, tibia or both — resulting from developmental variation, fracture, surgery or growth plate injury. Functional LLD occurs when the legs are structurally equal in length but biomechanical factors — excessive pronation, pelvic tilt, hip contracture, scoliosis — create an apparent discrepancy in how the body functions under load.
Distinguishing between the two is essential because the interventions are different. A podiatrist is well placed to identify functional contributors and address them directly, and to provide heel raise therapy for true LLD as part of a wider management plan.
Developmental variation
The most common cause of true LLD. Minor asymmetries in limb growth are extremely common and often go unnoticed until load-related symptoms develop in adulthood.
Fracture or surgery
Femoral or tibial fractures, hip replacement, knee replacement and growth plate injuries can all result in a structural change in limb length — either shortening or, less commonly, lengthening.
Overpronation
Excessive pronation at the subtalar joint functionally shortens the leg on the pronating side by collapsing the medial arch and internally rotating the tibia — a very common functional LLD driver.
Pelvic tilt
Muscle imbalance or hip flexor tightness causing a tilted pelvis creates an apparent leg length difference even when the bones are structurally equal. Often seen in runners and desk workers.
Hip pathology
Hip osteoarthritis, labral tears and femoroacetabular impingement can alter hip mechanics and produce a functional LLD through altered load transfer and compensatory movement patterns.
Scoliosis
Lateral curvature of the spine alters pelvic alignment and can create both structural and functional leg length differences depending on the degree and location of the curve.
LLD rarely presents as obvious limping in mild to moderate cases. More commonly, patients present with pain at a seemingly unrelated site — and only on careful assessment is the leg length difference identified as the underlying driver. Symptoms are typically asymmetric, affecting the longer or shorter leg depending on the compensation strategy adopted.
Unilateral or asymmetric low back pain, often worse after standing or walking
Hip pain — typically on the long-leg side from increased compressive load
Knee pain — often on the short-leg side from hyperextension compensation
Plantar fasciitis or heel pain — commonly on the short-leg side
ITB syndrome or lateral hip pain from pelvic drop on the short-leg side
Shin splints or stress fractures — asymmetric bone stress from unequal loading
Uneven shoe wear — one heel wearing significantly faster than the other
Feeling of one hip being higher than the other when standing
Accurate classification of LLD type is the essential first step — treating a functional LLD with a heel raise, for example, can worsen rather than improve symptoms. Our assessment combines clinical measurement, biomechanical examination and gait analysis to determine the nature, magnitude and functional significance of the discrepancy.
01
Clinical measurement. Tape measure assessment from ASIS to medial malleolus, block test standing measurement, and prone tibial and femoral segmental comparison to localise any true structural difference.
02
Biomechanical examination. Assessment of subtalar joint pronation, hip range of motion, pelvic tilt, hip flexor and abductor length — to identify functional contributors that may be creating or amplifying the apparent discrepancy.
03
Gait analysis. On Form joint tracking and video analysis to observe pelvic drop, trunk lean, asymmetric foot strike and compensatory patterns under dynamic load — often more revealing than static measurement alone.
04
Imaging referral. Where true structural LLD is suspected and precise measurement is required — particularly before orthotic heel raise prescription — we can arrange a scanogram or EOS imaging referral for accurate bone length quantification.
Management is determined by LLD type, magnitude and the symptom pattern. Small discrepancies (under 10mm) are often well managed conservatively; larger true differences may require a graded heel raise programme or multidisciplinary input.
LLD is frequently missed as a contributing factor in chronic lower limb pain — particularly when symptoms appear at a site distant from the pelvis. If you have persistent unilateral pain that has not responded to standard treatment, asymmetric shoe wear, or a history of lower limb fracture or hip/knee surgery, a structured assessment to rule out LLD is worthwhile.
Do not self-prescribe a heel raise without a formal assessment. Inserting a lift under the wrong leg, or introducing one too rapidly, can worsen symptoms and create new compensatory patterns. The magnitude, side and rate of introduction all need to be clinically determined.
How much of a difference actually matters?
This varies between individuals. Discrepancies under 5mm are rarely symptomatic in sedentary people but can be clinically significant in runners or those on their feet all day. Differences of 10mm or more are generally considered significant enough to warrant management regardless of activity level. The key is whether the discrepancy is producing compensatory patterns and load-related symptoms — not just its absolute size.
Can a heel raise make things worse?
Yes — if inserted on the wrong side, introduced too quickly, or used to treat a functional rather than true LLD. This is why clinical assessment before any heel raise prescription is essential. We typically introduce raises in 2–3mm increments with a period of adaptation between each stage.
Will I need to wear a heel raise forever?
For true structural LLD — yes, in most cases, as the underlying bone length difference does not change. For functional LLD, the goal is to address the underlying driver — pronation, pelvic tilt, hip weakness — so that the apparent discrepancy resolves and long-term orthotic dependency is minimised.
My GP said my legs are the same length but I still have symptoms — can I still have LLD?
Yes — functional LLD will not show up on a simple tape measure test or X-ray if it is driven by pronation or pelvic mechanics rather than bone length. Many patients with functional LLD are told their legs are equal length, when in fact a significant apparent discrepancy exists under dynamic load. A full biomechanical assessment is needed to identify this.
Is LLD covered by insurance?
Assessment and management as part of a podiatry consultation is typically covered by Bupa, Vitality, AXA PPP, Cigna, Aviva, WPA and Simply Health. Orthotics and heel raises are generally not covered by UK insurers. We recommend confirming with your insurer before booking.
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