Leg Length Discrepancy

Written by: Dr Jeremy Steinberg – created: 15 April 2022; last modified: 4 September 2025

This article is still missing information.

Leg Length Discrepancy
Epidemiology	59% having an LLD of at least 5mm.
Validity	Controversial relation to pain
Treatment	Shoe lifts, surgery

Leg length discrepancy also known as leg length inequality refers to unequal lower limb lengths. Even discrepancies of 5-10mm in susceptible individuals may a factor for pain in hip osteoarthritis, knee osteoarthritis, chronic low back pain, and even headaches.

Inequality in leg length is commonly associated with compensatory gait abnormalities and may lead to degenerative arthritis of the longer lower extremity and lumbar spine. LLD may be a source of pain and disability.

Aetiology

Anatomic: This refers to LLD due to fracture, trauma or tumour of the growth plate, degenerative disorders, post arthroplasty, Legg-Calvé-Perthes disease, arteriovenous fistula, vascular tumours, post hip arthroplasty.

Developmental: From congenital aplasia, hypoplasia, developmental dysplasia of the hip, clubfoot, hemihypertrophy syndromes, clubfoot

Function: This refers to joint contracture, soft tissue shortening, ligamentous laxity, axial malalignment, and abnormal foot mechanics. For instance, flexion contractures at the knee and hip can make a leg functionally shorter, while an equinus deformity of the ankle can make it functionally longer.

Environmental: repeated exposure to uneven ground such as repeated running on a cambered road.

Biomechanics

The biomechanics were reviewed and assessed by Kakushima et al. They found that there was an asymmetrical lateral bending motion during heel-raising gait as compensation for the LLD.

Even relatively small discrepancies (5–10 mm) can alter biomechanics and require compensatory adjustments in posture and gait. The body will typically tilt the pelvis down on the shorter side, leading the lumbar spine to bend toward the longer leg to keep the shoulders and head level . This compensatory pelvic obliquity and lumbar curvature (a form of functional scoliosis) can propagate up the kinetic chain. Hip adduction on the long side and ankle plantar-flexion on the short side stabilise the centre of mass. Repetitive asymmetric loading elevates shear across the sacroiliac joints and increases ground-reaction forces through the longer limb, predisposing that side to articular degeneration.

Over time, these adaptations may strain muscles and joints asymmetrically and have far-reaching effects beyond the lower limbs.

Classification

Severity:

• Mild: <30mm. Often asymptomatic; lift therapy usually sufficient.
• Moderate: 30-60mm. Shoe raise or orthosis is recommended; consider guided growth in skeletally immature patients.
• Severe: >60mm. High likelihood of gait asymmetry, pelvic tilt, compensatory scoliosis, and degenerative change.

It can also be classified as

• structural: true bony length difference
• functional: legs equal in length but appearing unequal due to pelvic tilt, spinal curvature, or muscle imbalances.

Epidemiology

LLD is present in up to 90% of the population, with 59% having an LLD of at least 5mm.

Assessment

The use of accurate and reliable methods for quantifying LLD is vital for planning the right treatment. While clinical methods are useful for screening, imaging modalities are considered more accurate

Inspection: Look for a compensatory scoliosis or pelvic obliquity. This often begins by observing the patient from behind, looking at the levels of the posterior superior iliac spines (PSIS), inferior gluteal folds, and popliteal creases. Each anatomic landmark should be at approximately the same level. If a LLD exists then one hip usually appears lower than the other.

Tape Measure Method: This is a common screening tool. The True leg length is measured directly from the ASIS to the medial malleolus, with the tape running medial tot he patella. The apparent length is measured from the umbilicus to the medial malleolus to account for pelvic obliquity. The tape measure method can be inaccurate due to: obesity, angular deformities, difficulty palpating landmarks.Relying on the average of two separate measurements is encouraged to improve reliability.

Standing Block Method: In this "indirect" method, blocks of a known height are placed under the shorter limb until the pelvis is level. This technique is generally considered slightly more reliable and accurate than the tape measure and can help determine the functional correction a patient finds comfortable. A compensatory scoliosis usually disappears when the LLD is corrected by placing a block under the shorter leg.

Imaging

Imaging provides a more accurate and reliable analysis of LLD compared to the clinical exam.

Teleoroentgenogram (Full-Length Standing Radiograph): This is a single, full-length standing X-ray of both lower extremities. It is the recommended primary imaging modality for the initial evaluation of LLD. Its advantages include it being comprehensive (visualisation of entire lower limb which is helpful for angular deformities), lower radiation, and cost-effective).

Scanogram: This technique uses three separate, tightly focused X-ray exposures centered on the hip, knee, and ankle to minimize measurement errors from magnification. However, it is performed with the patient lying down (supine) and has several drawbacks, including a higher radiation dose and an inability to assess angular deformities or discrepancies in foot height.

CT Scanogram: This method uses a digital scout view from a CT scanner to measure limb length. It is highly accurate and reliable, with significantly less radiation exposure than plain radiography. A lateral CT scanogram is especially useful for patients with flexion contractures at the knee, where other methods may underestimate the true length.

Treatment

There is low quality evidence that shoe lifts reduce pain and improve function in patients with LLD and associated painful musculoskeletal conditions. The percentage correction varies between studies. Trailing 50% correction may be a good starting point. Surgery can be considered if the discrepancy is over 25mm.

Heel Lifts: For structural LLD, adding a lift to the shoe of the shorter leg is a simple way to level the pelvis.

Custom Foot Orthotics: Orthotic insoles can correct foot malalignments (like overpronation or arch collapse) that contribute to functional LLD or general postural instability. If an orthotic corrects foot alignment but does not account for a true leg-length discrepancy, it might inadvertently worsen cervical tension because of the loss of adaptation. For example the longer leg may develop a compensatory pes planus to functionally shorten the leg, if you correct the foot arch alone without also raising the shorter contralateral leg the patient may feel worse.

Resources

Shoe lifts for leg length discrepancy systematic review - Campbell 2017- 355 KB (f)

Leg length discrepancy - Sabharwal 2008.pdf- 379 KB (f)

Leg length discrepancy - Khalifa 2017.pdf- 337 KB (f)

Literature Review

Literature Review

Reviews from the last 7 years: review articles, free review articles, systematic reviews, meta-analyses, NCBI Bookshelf

Articles from all years: PubMed search, Google Scholar search.

TRIP Database: clinical publications about evidence-based medicine.

Other Wikis: Radiopaedia, Wikipedia Search, Wikipedia I Feel Lucky, Orthobullets,