A method of repair for anteromedial rotatory instability of the knee is described and the results of operations on 36 knees reviewed. Complete static correction occurred in 30 of these patients (84 per cent), three patients showed improvement (8 per cent) and three showed no improvement (8 per cent). Although the operation was not reliable as a correction for valgus instability, it did not increase this instability. This operation may be combined with other procedures to correct all instabilities or problems of the knee.