Asymmetric limb loading with true or simulated leg-length differences.

Unequal leg lengths result in asymmetric limb loading but opinions vary on the size of the difference inducing abnormal loading, and which limb sustains the greater load. Our study compared limb-loading asymmetries during walking for subjects with anatomic leg-length discrepancies between 1.0 and 3 cm, subjects without length discrepancies, and for subjects with a simulated a 1.31-cm leg-length discrepancy. Symmetry indices were calculated for peak ground reaction force during weight acceptance, rate of change of weight acceptance force, peak push-off force, and rate of change of push-off force. All symmetry measures were significantly different from normal for the simulated leg-length discrepancy. The shorter limb sustained a greater proportion of the load and loading rate. The anatomic leg-length discrepancy group showed the same trend with the exception of the push-off force rate. There were equivalent size-effect differences for both leg-length discrepancy conditions; however, for the anatomic leg-length discrepancy group, only the weight acceptance force symmetry value was statistically different from normal. The shorter limb sustains a greater proportion of load and loading rates; therefore, equalizing leg lengths should be considered even with bilateral differences less than 3 cm.