SURGICAL-CORRECTION OF LEG ALIGNMENT IN UNILATERAL KNEE OSTEOARTHROSIS REDUCES THE LOAD ON THE HIP AND KNEE-JOINT BILATERALLY

Seventeen patients with strictly unilateral medial knee osteoarthrosis that justified surgical treatment constituted the study group. No pat ient had any symptoms from the hip or ankle joints or from the other k nee. Eight patients were operated with high tibial osteotomy and nine were operated with unicompartmental prosthetic replacement (Brigham mo del). The forces and the external moment about the hip, knee, and ankl e joints of the involved and uninvolved leg were calculated before and 1 year after corrective surgery and compared to the external moment i n 10 normal controls. Clinical examinations was performed and the hip- knee-ankle angle in the involved leg was determined from whole-leg wei ghtbearing radiographs before and 1 year after surgery. The external m oments about the hip, knee, and ankle joints and the knee moment arms at mid-stance in the frontal plane during gait were determined with a Kistler force plate and a videorecording system. All patients improved clinically after surgery. The mean hip-knee-ankle angle changed from 11 degrees of varus to 0 degrees. In the uninvolved leg the mid-stance adduction moments about the hip and knee joints were significantly in creased compared to normal subjects in the control group before surger y, but reduced to a normal level 1 year after surgery. This reduction was mainly due to a significant reduction of the medially directed for ce. The moments about the ankle joints were not found to be changed by the knee deformity or by the corrective surgery.