Leg length discrepancy: how to measure it precisely and why an orthosis with a heel raise changes the picture
"You have one leg shorter than the other" is a phrase many people hear at some point. Most have a minimal, asymptomatic difference. But when there is low back pain, postural scoliosis or one-sided overload, in anyone, sedentary or athletic, the question changes: exactly how large is that difference, and does compensating it properly change the picture?
Functional vs anatomical: why the distinction matters
A leg length discrepancy can be anatomical (the actual bone lengths of the lower limb differ between the two sides) or functional (the bones are equal but posture, the pelvis or the way you walk create an apparent difference). The treatment approach differs: an anatomical discrepancy usually calls for a heel raise in the shoe or orthosis; a functional one calls for treating the cause (pelvic mobility, motor control, gait). Telling the two apart is the first clinical step.
Why accurate measurement matters
Above 20 mm the biomechanics change
Clinical review of the impact of leg length discrepancy: differences below 10 mm are usually asymptomatic, but discrepancies above 20 mm alter biomechanics and loading patterns, cause functional limitations and lead to functional scoliosis, which over time drives degenerative changes in the lumbar facets and discs.
The clinical message: a leg length discrepancy sustained over time is not a trivial finding; it modifies the load on the spine and on the joints of the whole chain. In the presence of symptoms, assessment should be objective and the decision to compensate individualised.
Applebaum A, Nessim A, Cho W. Overview and Spinal Implications of Leg Length Discrepancy: Narrative Review. Clin Orthop Surg. 2021;13(2):127-134. doi:10.4055/cios20224
How we measure it: photogrammetry with passive markers
Reliability equivalent to the biomechanical gold standard
Study in 30 volunteers evaluating a photographic system with passive markers on anatomical landmarks (iliac spines, trochanters, femoral condyles) against a reference optoelectronic system (SMART-DX 700 BTS): excellent reliability with ICC 0.92-0.99 and SEM 0.78°-3.33°, equivalent to the gold standard, with shorter processing time.
This is exactly the method we use in clinic: passive markers on anatomical landmarks (iliac spines, trochanters, femoral condyles, malleoli), a calibrated photograph and analysis with clinical software. The protocol is non-invasive, repeatable at successive follow-ups and provides a reliable millimetre-level measurement, without radiation.
Temporiti F, Adamo P, Mandelli A, Buccolini F, Viola E, Aguzzi D, et al. Test-retest reliability of a photographic marker-based system for postural examination. Technol Health Care. 2023;31(4):1153-1160. doi:10.3233/THC-220155
A single photograph is reliable enough
Reproducibility study of photogrammetric postural assessment in 24 healthy subjects, using digital image software. Excellent ICCs for all variables; standard error of measurement and minimal detectable change below 5% within-day; between-day reproducibility from 0.9% to 12.5% depending on the variable.
The practical clinical conclusion: a single photograph reliably represents the patient's static posture. This makes it possible to repeat measurements at successive follow-ups with real precision and to verify objectively whether the compensation with a heel raise is producing the expected effect.
Candotti CT, Gelain GM, Antoniolli A, Araújo LM, Vieira A, Loss JF. Repeatability and Reproducibility of Postural Variables by Photogrammetry. J Manipulative Physiol Ther. 2019;42(5):372-378. doi:10.1016/j.jmpt.2018.10.006
When to compensate, and by how much
A clinical decision guided by thresholds, made case by case
Authoritative European clinical review of treatment indications and strategies. Pragmatically: below 5-10 mm most people compensate physiologically without treatment; between 10-20 mm with symptoms, compensation with a heel raise or orthosis is considered; above 20 mm or with a clear clinical impact, progressive partial compensation.
The authors stress that the decision is not made on the millimetre alone: it depends on symptoms, age, activity and the clinical response to conservative treatment. The choice between a shoe lift, an orthosis with an integrated heel raise or surgery (in very severe discrepancies) is tailored case by case.
Vogt B, Gosheger G, Wirth T, Horn J, Rödl R. Leg Length Discrepancy, Treatment Indications and Strategies. Dtsch Arztebl Int. 2020;117(24):405-411. doi:10.3238/arztebl.2020.0405
The heel raise, with evidence: pain relief in 88% of patients
Heel raises in adults with LLD and pain: relief in most
Systematic review of 10 studies of shoe lifts in adults with leg length discrepancy associated with low back pain, scoliosis or hip and knee osteoarthritis. 88% ± 3% of 349 patients treated with a lift obtained partial or complete pain relief (range 66.7-100%). In the included RCT, every treated patient experienced relief, with a mean reduction of 27 ± 9 mm on a 150 mm VAS.
This is the key reference supporting the use of a heel raise when leg length discrepancy is associated with musculoskeletal pain. The quality of the evidence is heterogeneous, and the authors call for more RCTs, but the direction and consistency of the benefit are clear.
Campbell TM, Ghaedi BB, Tanjong Ghogomu E, Welch V. Shoe Lifts for Leg Length Discrepancy in Adults With Common Painful Musculoskeletal Conditions: A Systematic Review of the Literature. Arch Phys Med Rehabil. 2018;99(5):981-993.e2. doi:10.1016/j.apmr.2017.10.027
Custom orthosis with 100% correction
NPRS 7.8 → 0 at 2 years with a customised orthosis
Prospective observational study in 80 patients with non-specific low back pain and leg length discrepancy treated with a customised orthosis correcting 100% of the LLD (integrated heel lift) and postural assessment by 3D stereophotogrammetry. Baseline NPRS 7.8; 1.1 at 4 months; 0 at 2 years. Significant improvements in postural symmetry and plantar loading; no contraindications.
The clinical message is direct: when the correction is dosed to 100% of the measured discrepancy and built into a customised orthosis, the effect on pain is clinically very relevant and holds over time. The differential factor is not the heel raise on its own, it is the millimetre-level personalised correction built into an orthosis designed for the patient.
D'Amico M, Kinel E, Roncoletta P. Leg Length Discrepancy and Nonspecific Low Back Pain: 3-D Stereophotogrammetric Quantitative Posture Evaluation Confirms Positive Effects of Customized Heel-Lift Orthotics. Front Bioeng Biotechnol. 2022;9:743132. doi:10.3389/fbioe.2021.743132
Mechanism: better kinematics, less pain
Low back pain reduction correlated with improved ankle kinematics
After 3 weeks wearing an orthosis with an integrated heel raise, patients with mild leg length discrepancy (≤2 cm) showed a significant reduction in low back pain (p<0.05) correlated with improved ankle kinematics during walking (p=0.02; r=0.80).
Biomechanical adaptation is individual: each patient compensates differently. That is why an orthosis with a heel raise is not a generic product; the dose is adjusted to the case, re-evaluated and fine-tuned at clinical follow-up.
Menez C, Coquart J, Dodelin D, Tourny C, L'Hermette M. Effects of Orthotic Insoles on Gait Kinematics and Low-Back Pain in Patients with Mild Leg Length Discrepancy. J Am Podiatr Med Assoc. 2021;111(4). doi:10.7547/18-093
Take-home
- Most leg length discrepancies are small and asymptomatic; they matter when there are symptoms or when they exceed certain thresholds.
- Distinguishing anatomical from functional discrepancy is the first clinical step; it completely changes the treatment.
- Precise measurement with photogrammetry and passive markers on anatomical landmarks is the modern clinical standard: reliability equivalent to reference optoelectronic systems, with millimetre precision.
- A well-dosed, customised orthosis with a heel raise reduces pain in a clinically relevant, sustained way, especially when the correction is dosed at 100% and built into a personalised orthosis.
How Avanza Salud can help
We manage leg length discrepancy with a rigorous protocol from the first visit: a photogrammetric biomechanical assessment with passive markers on the relevant anatomical landmarks (iliac spines, trochanters, femoral condyles, malleoli) and analysis with millimetre-calibrated software, a clear distinction between anatomical and functional discrepancy, custom Podonexus orthoses with a heel raise dosed exactly to your case, and clinical follow-up with objective re-measurement to verify the improvement and adjust it if needed. If you have long-standing low back pain, postural scoliosis, one-sided hip or knee pain, or you suspect one leg is shorter, it is worth having an assessment with a real measurement before buying any generic heel raise.