[On the cause of the anterolateral instability of the knee joint. A study on 20 cadaver knee joints with special regard to the tractus iliotibialis (author's transl)].

Experiments on 20 cadaver knee joints are reported on. A short medial incision was made to transect the anterior cruciate ligament. Through a long lateral incision the lateral structures (lateral capsule, lateral collateral ligament, and iliotibial tract) were transected in variable series to check their influence on the pivot shift-sign. The results are tabulated. The anterior cruciate ligament is shown to be the key structure for the pivot shift-sign. This sign is only markedly positive when the lateral structures are intact. Depending on the pattern of transection of the lateral structures the pivot shift-sign is less marked or totally absent. It is also shown why this sign is missing in the unhappy triad. Because the intact distal part of the iliotibial tract is responsible for the pivot shift-sign, a detailed description of its anatomy and physiology is given.