Knee instability before and after high tibial osteotomy.

Knee joints were examined by three-point measurement (Edholm et al. 1976, 1977). The instability in arthrotic joints did not differ significantly from that in normal knees, but the varus/valgus deviation as measured by the three-point technique differed significantly from that in normal knees. After high tibial osteotomy for varus malalignment the instability increased significantly. An increase of more than 2 degrees was associated with significantly poorer subjective results of operation. The findings indicate that shortening of the lateral stabilizing structures of the knee joint should be carried out in connection with high tibial osteotomy for varus malalignment. No upper limit of preoperative instability consistent with a good result of operation was established.