Moments and muscle activity after high tibial osteotomy and anterior cruciate ligament reconstruction

PURPOSES: To evaluate the effects of simultaneous high tibial osteotomy (HTO) and anterior cruciate ligament (ACL) reconstruction on 1) the external knee adduction moment, 2) the external knee flexion and extension moments, and 3) the quadriceps, hamstrings, and gastrocnemius muscle activity during walking. METHODS: Twenty-one patients with varus malalignment of the lower limb, medial compartment knee osteoarthritis, and concomitant anterior cruciate ligament (ACL) deficiency were tested before and 1 yr after undergoing simultaneous medial opening wedge high tibial osteotomy (HTO) and ACL reconstruction during a single operation. Three-dimensional kinetic and kinematic data were used to calculate external coronal and sagittal moments about the knee. EMG data from the quadriceps, hamstrings, and gastrocnemius were used to determine coactivation ratio and activation patterns. RESULTS: Neutral alignment and knee stability were achieved in all patients after surgery. The peak knee adduction moment decreased from 2.88 ± 0.57 to 1.71 ± 0.56%BW×-Ht (P < 0.001). The early stance knee flexion moment decreased from 1.95 ± 1.89 to 0.88 ± 1.17%BW×-Ht (P < 0.01). The late stance knee extension moment increased from 1.83 ± 1.53 to 2.76 ± 1.22%BW×-Ht (P < 0.001). There were no significant differences in muscle coactivation or muscle activation patterns (P > 0.05). CONCLUSIONS: Improving lower limb alignment and knee stability significantly alters the coronal and the sagittal moments about the knee during walking, without apparent changes in muscle activation patterns.