Leg Length Discrepancy: The Natural History (And What Do We Really Know)

Background: The long-term effects of small limb length discrepancies have been poorly documented in the literature. References to low back pain, hip pathology, knee pathology, and foot problems abound in the popular literature. Health care providers frequently recommend the use of lifts for structural and functional limb length discrepancies, yet the natural history of limb length inequality as well as the effectiveness of treatments that may be recommended are obscure. The purpose of this paper is to document and evaluate the literature associated with small limb length discrepancies. Methods: A search of the English literature was carried out using PubMed to identify papers dealing with the effects of limb length discrepancies. Papers reporting only expert opinion or case reports were excluded. Results: Papers dealing with the natural history of limb length discrepancy as well as studies in which gait analysis was performed in patients with limb length discrepancy were identified. Only 10% of the population has exactly equal lower limb lengths. Approximately 90% of the population has a limb length discrepancy <1.0 cm. Hip and knee pathology is present in an increased number of patients with limb length discrepancies over 5 mm. Hip pathology is more often present in the long leg, knee pathology has been reported in various studies to be more common in either the long or short leg. Low back problems seem to be more common on the short side in patients with limb length discrepancies. A number of different compensatory mechanisms for limb length discrepancy have been identified during gait analysis. Conclusions: There seems to be a consensus that limb length discrepancies >2.0 cm are frequently a problem. There is some evidence that limb length discrepancies as little as 5 mm can lead to long-term pathology.