Change in adduction moment about the knee after high tibial osteotomy and prosthetic replacement in osteoarthrosis of the knee.

Fifty-three patients with moderate medial osteoarthrosis of the knee were studied before and after corrective surgery. Twenty-five patients were treated with high tibial osteotomy and 28 with unicompartmental prosthetic replacement (Brigham model). The external moments about the knee were calculated and correlated to the hip-knee-ankle angles before and 1 year after corrective surgery. The hip-knee-ankle angle was determined from whole-leg weightbearing radiographs before and 1 year after surgery. The peak adduction moment and' the mid-stance adduction moment about the knee in the coronal plane during gait were determined with a Kistler force plate and a videorecording system. Surgical correction of leg alignment measured with the hip-knee-ankle angles were achieved in both groups. After surgery the mean hip-knee-ankle angle was changed from 9° of varus to 3° of varus in the prosthetic group and from 9° of varus to 4° of valgus in the osteotomy group. The mean peak knee adduction moment was reduced from 66 N m to 47 N m in the prosthetic group (P < 0.01) and from 63 N m to 21 N m in the osteotomy group (P < 0.001). The' mean mid-stance knee adduction moment was reduced from 48 N m to 27 N m in the prosthetic group (P < 0.001) and from 47 N m to 13 N m in the osteotomy group (P < 0.001). There was an association between the change in adduction moments about the knee and the change in hip-knee-ankle angle after surgery (r = 0.45, P < 0.001). In conclusion our results show that correction of leg aligment will reduce the adduction moments about the osteoarthrotic knee during gait.