The Anterolateral Ligament of the Knee: A Proposed Classification System

The anterolateral ligament (ALL) is a potential stabilizer of the knee and cooperates with the anterior cruciate ligament (ACL). It originates on the lateral epicondyle of the femur, to which it is mainly posterior and proximal; insertion is posterior to Gerdy's tubercle. Its anatomical characteristics vary. Recent publications have focused on morphological variations concerning mainly the femoral and tibial attachments, and on morphometric measurements. Histological and cystochemical examinations have also been performed. Classical anatomical dissection was performed on 111 lower limbs (25 isolated and 86 paired) fixed in 10% formalin. The knee region was dissected using traditional techniques and the morphological features of the ALL were assessed: morphometric measurements and the types of ALL. The ALL was present in 70 individuals (37 woman and 33 men). In 30 cases, it was absent symmetrically, and in 11, it was present on just one side (P = 0.0011). The ALL was morphologically very variable. In type I (the most common form - 64.3%), a single band traveled parallel to the fibular collateral ligament (FCL); in type II the band crossed it. In type III, the origin was located on the lateral epicondyle of the femur and also on the lateral-posterior surface of the joint capsule, and the insertion was in the deep fascia of the leg: this type could be called a capsule. Type IV was characterized by a double ALL, type IIb by ligaments that bifurcated, and type V by the ALL starting directly from the FCL rather than the femoral epicondyle. The ALL is characterized by high morphological variability, both in its femoral and in its tibial attachments and in its course. Clin. Anat. 31:966-973, 2018. © 2018 Wiley Periodicals, Inc.