The importance of submalleolar deformity in determining leg length discrepancy

Background and purpose: The association of leg length discrepancy (LLD) with a number of clinical disorders has made its determination a significant part of the physical examination. We believe that submalleolar causes of LLD may be under-acknowledged. The most common clinical method used to measure LLD is by tape from the anterior superior iliac spine (ASIS) to medial malleolus which disregards the potential for LLD arising from asymmetry in the foot distal to the tibiotalar joint. Methods: The present pilot study involves a group of 5 volunteers (experimental group) and a group of 3 patients with flexible flat feet (clinical study). The differences in tibial tubercle height from the ground between full pronation and full supination were measured using the CODA MPX 30^® system (Charnwood Dynamics Limited, Leicestershire, England). Correlations of the patterns within each group were produced. Results: A significant relationship with leg lengths was found in the experimental group when they induced maximum pronation (R-squared=0.62, p=0.007) while an inverse relationship occurred with supination, although marginally significant (R-squared=0.37, p=0.064). Conclusions: We have demonstrated that significant leg length discrepancy can occur in patients who do not have obvious deformity when non weight bearing. We recommend using the blocks method routinely. Appropriately measuring LLD is of vital importance to properly diagnosing and treating patients with unequal leg lengths or related symptoms.