Previous research suggests knee joint moments and muscle activity during walking are altered in patients with anterior cruciate ligament (ACL) deficiency and in patients with medial compartment knee osteoarthritis (OA). The objective of this study was to compare knee joint flexion and adduction moments and the extent of quadriceps-hamstring muscle co-contraction before and one year after combined simultaneous ACL reconstruction and high tibial osteotomy (HTO).

Eighteen patients (three females, fifteen males; age = 40 ± 8 yrs.; BMI = 28.8 ± 5.77) with ACL deficiency and OA affecting primarily the medial compartment of the knee underwent ACL reconstruction (hamstring autograft) and medial opening wedge HTO procedures during a single operation. All patients completed pre-operative and one-year postoperative quantitative gait assessments. Three-dimensional kinetic and kinematic data were collected during self-paced walking and used to calculate the peak external flexion and adduction moments about the knee. Electromyographic (EMG) activity was collected from the hamstrings and quadriceps and used to calculate the co-contraction ratio. Peak moments and co-contraction ratios were compared pre and postoperatively using paired t-tests.

The peak knee flexion moment decreased from 2.31 ± 1.14 to 1.33 ± 0.73 %BW*ht (p=0.001); mean decrease = 0.98 %BW*ht (95%CI: 0.49–1.47). The peak knee adduction moment decreased from 2.81 ± 0.62 to 1.69 ± 0.61 %BW*ht (p< 0.001); mean decrease = 1.12 %BW*ht (95% CI: 0.80–1.43). The quadriceps-hamstring co-contraction ratio decreased from 0.82 ± 0.14 to 0.72 ± 0.18 (p=0.056); mean decrease = 0.10 (95% CI: −0.003 – 0.21).

The present findings suggest that combined simultaneous ACL reconstruction and HTO significantly decreases knee flexion and adduction moments during walking. Although the present findings suggest that the quadriceps-hamstring co-contraction ratio also decreases, future research with more patients is required to confidently evaluate potential changes in muscle activity. These findings are consistent with an overall reduction in dynamic knee joint load.