The rotation and tibial torsion of the leg in osteoarthritis (15 cases) were investigated using the computed tomography, and the results of osteoarthritis (O. A.) group were compared with those of the Intact group (8 cases). The different angles of the rotation of the leg measured in three positions (rest, neutral and quadriceps setling) were especially investigated. The results are as follows:
1) The O. A. group showed slight internal rotation and tibial internal torsion in all three positions, however, there was no statistically significant difference comparing with the Intact group.
2) The O. A. group without flexion contracture showed significantly different angles between three positions.
3) It is suggested that the rotational instability of the knee joint has to be considered for planning the programs of therapeutic exercise for the osteoarthritic knee.