Change of adduction moment about the hip, knee and ankle joints after high tibial osteotomy in osteoarthrosis of the knee.

The purpose of this study was to investigate the change of load about the knee joint and the ipsilateral hip and ankle joints in the coronal plane after high tibial valgus osteotomy in nine patients, mean age 64 years, mean weight 81 kg, with moderate medial osteoarthrosis of the knee, compared to ten age-matched normal controls. Moments about the joints were assessed with a computerized Kistler force platform and a videorecording system before surgery, and 6 and 12 months after surgery. Loads in the joints are related to the peak and midstance external adduction moments and the area under the moment curve. In patients before surgery there was a significantly increased adduction moment in both the hip and knee joints compared to the normal controls. After surgery the adduction moment was reduced to subnormal levels in the knee and normal levels in the hip joint. The moments about the ankle joint were unaffected both by the knee deformity and by the corrective surgery. This study demonstrates that a varus malalignment in the osteoarthrotic knee is accompanied by increased load about the ipsilateral hip. We do not know if this increased load about the hip has any pathological significance, but one might suspect a more rapid progression of degenerative changes in the hip joint cartilage as a consequence of the increased load. We have also found that the frontal plane moment about the hip can be reduced to a normal level when the knee is changed into slight valgus. The reduced load might be beneficial to a patient with osteoarthrosis of the ipsilateral hip and knee.