The Anterolateral Ligament of the Knee: Descriptive Anatomy and Clinical Correlation

The anterolateral ligament is a fibrous structure in the anterolateral aspect of the knee. Recently this liagament of the knee has gained spotlight in anatomical and imaging studies and has been designated as a new ligament of the knee joint. The anterolateral ligament (ALL) has been postulated to be a restraint against the anterolateral instability of the knee resulting in a positive pivot shift test. The purpose of this study is to provide detailed anatomical characteristics of ALL in the Indian population.

The qualitative and quantitative characteristics of the ALL were observed in 20 embalmed cadaveric specimens. In all but one left male knee specimen (95%) ALL was observed. After isolating the ALL, its length, thickness, width, and points of attachments and dimensions of lateral collateral ligament (LCL) were determined.

The ALL was consistently present in the anterolateral region of the knee separate from the joint capsule. Its proximal attachment to the femur is anterior and distal to the attachment of the LCL. Distally the superficial fibers of the ALL inserted close to the Gerdy's tubercle at the level of the fibular head, and the deeper fibers merged with the lateral meniscus. The mean length of the ALL was 43.35 mm ± 4.04 mm in flexion and 40.38 mm ± 4.35 mm in extension. The average width of the ALL was 6.98 mm ± 0.95 mm at its origin and 9.36 mm ± 1.07 mm at its insertion.

The ALL is hypothesized to affect internal tibial rotation and plays a role in the pivot shift phenomenon. ALL rupture could be responsible for rotatory laxity after isolated intraarticular reconstruction of the ACL.