Effect of Leg-length Discrepancy on Lower-limb Muscle Activities during Gait: Focus on Equinus Gait

[Purpose] To clarify the changes in the activities of muscles involved in a strategy for leg-length discrepancy, focusing on equinus gait. [Subjects] The subjects were 10 healthy persons with no leg length discrepancy. [Methods] To artificially create leg-length discrepancy gait, a wedge was placed under the sole of one foot, and surface electromyography (sEMG) was used to measure the activities of the lower limb muscles thought to be involved in equinus gait, and the results were compared with normal gait. [Results] A significant increase in the activity of the tibialis anterior was seen at a wedge thickness of 3 cm, and significant increases in the activities of the rectus femoris, tibialis anterior, and gastrocnemius were seen at a wedge thickness of 4 cm. [Conclusion] Hyperkinesia was found in the muscles considered to be involved in equinus gait resulting from leg-length discrepancy. This gait change and the possible occurrence of additional functional disorders would benefit from physical therapy interventions for leg-length discrepancy.