Morphology of the anterolateral ligament: a complex of fibrous tissues spread to the anterolateral aspect of the knee joint.

The anterolateral ligament (ALL) has recently received considerable attention as a key structure maintaining the rotational stability of the tibia. However, the morphology of the ALL, particularly the proximal attachment, is controversial. This study aimed to elucidate the morphological relationship between the ALL and its adjacent structures. A total of 25 knees from 22 cadavers were used in the current study. One knee was set at 30°, 60° and 90° of flexion. Stretched or winkled fibrous tissues were then observed with internal and external rotations of the tibia at each angle. In 22 knees, fibrous tissues that were attached to the lateroposterior area to the Gerdy's tubercle were macroscopically observed. In the other 2 knees, the fibrous tissues were histologically investigated and analyzed using computer-assisted three-dimensional reconstruction. A taut fibrous tissue was observed between the lateroposterior area to the Gerdy's tubercle and the posterosuperior area to the lateral epicondyle during an internal rotation of the tibia. A complex of fibrous tissues that were attached to the lateroposterior area to the Gerdy's tubercle spread to the anterolateral aspect of the knee as a sheet-like structure. This complex tissue was composed of the fascia lata and fibrous tissues continuous from the fabellofibular ligament, intermuscular septum, and tendon of the gastrocnemius. Three-dimensional reconstruction showed that each fibrous tissue formed a sheet. The structure recognized as the ALL could not be detected; therefore, the ALL that has been reported to date is considered to be a complex of fibrous tissues with a sheet-like structure.