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 patient had any symptoms from the hip or ankle joints or from the other knee. Eight patients were operated with high tibial osteotomy and nine were operated with unicompartmental prosthetic replacement (Brigham model). The forces and the external moment about the hip, knee, and ankle joints of the involved and uninvolved leg were calculated before and 1 year after corrective surgery and compared to the external moment in 10 normal controls. Clinical examinations was performed and the hip-knee-ankle angle in the involved leg was determined from whole-leg weightbearing radiographs before and 1 year after surgery. The external moments 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 increased compared to normal subjects in the control group before surgery, but reduced to a normal level 1 year after surgery. This reduction was mainly due to a significant reduction of the medially directed force. The moments about the ankle joints were not found to be changed by the knee deformity or by the corrective surgery. RELEVANCE: This study demonstrates that a varus malalignment in the osteoarthrotic knee is accompanied by increased load about the uninvolved hip and knee joint. One might expect a more rapid progression of degenerative changes in joint cartilage as a consequence of such increased load. The reduced load after surgical correction of leg alignment might be beneficial to patients with osteoarthrosis of their hip and knee joints.