Effect of Leg Length Discrepancy on Dynamic Gait Stability.

Objectives: : It is unclear whether the increased center of mass lateral shift during gait induced by leg length difference induces lateral instability. The purpose of this study was to investigate the effect of leg length discrepancy (LLD) on dynamic gait stability and the compensatory kinematic and dynamic strategies for this effect by using the extrapolated center of mass and margin of stability.

Methods: : Nineteen healthy male participants walked without insoles (no LLD condition; 0 cm) and with added insoles (LLD condition; 3 cm). Kinematic and kinetic data were analyzed using a three-dimensional motion analyzer and force plates; the values were compared between the two conditions. Correlation analysis was performed on the parameters and the margin of stability and significant changes were identified.

Results: Compared with the no-LLD condition, in the LLD condition, lateral stability was maintained on both the short leg side and the long leg side. Nonetheless, changes in joint angles and muscle activity on the frontal plane were observed on the short leg side, although the correlations were not significant. On the long leg side, a moderate negative correlation was found between the lateral flexion angle of the trunk and the margin of stability (r=-0.56, P=0.011).

Conclusions: The short leg side may compensate for lateral stability by complex changes in joint angles and muscle activity, and the long leg side may compensate for lateral stability by actively adjusting the trunk lateral flexion angle.