Joint moments in minor limb length discrepancy: a pilot study

A biomechanical analysis was performed to determine if a minor limb length discrepancy alters lower extremity joint mechanics significantly and in a manner that could contribute to the development of joint abnormalities. Ten healthy subjects with equal limb lengths were recruited. Gait analysis was performed for both left and right sides to determine the maximum moments at the hip, knee, and ankle joints. A minor limb length discrepancy was simulated by adding a shoe lift of 1.25 cm to the left leg. After a period of acclimation, the gait was reanalyzed. Differences for maximum joint moments at the hip, knee, and ankle before and after simulation were nonsignificant. An additional 10 healthy, asymptomatic patients with actual limb length discrepancies ranging from 1 cm to 2 cm were also recruited. Gait analysis for maximum joint moments before and after correction of the limb length discrepancy was performed. Side-to-side differences in joint moments before correction were nonsignificant. After correction of the limb length discrepancy, side-to-side joint moment differences were significantly increased (P = 0.02) and may suggest acute overcompensation to the presence of the corrective shoe lift. Consequently, this study did not find an association between minor limb length discrepancies and predictable changes in lower extremity joint kinetics that might potentially lead to joint abnormalities.