Isometric Characteristics of the Anterolateral Ligament of the Knee: A Cadaveric Navigation Study

PurposeTo measure the variations in length during flexion and internal tibial rotation of the 3 different femoral insertions of the anterolateral ligament (ALL) while maintaining a fixed tibia insertion.MethodsTwelve fresh-frozen cadaver knees were analyzed using a navigation system. Maximal distance variations of the 3 different anatomic femoral insertions of the ALL were measured during knee flexion and internal tibial rotation at 20° (IR20°) and 90° (IR90°). The 3 different femoral attachments were, as published, at the center of the lateral epicondyle, distal and anterior from this position, and proximal and posterior. Each of these 3 femoral insertions was coupled to the same tibial insertion at the tibial margin, halfway between the tip of the fibular head and the prominence of the Gerdy tubercle.ResultsDuring IR20°, variation in the distance between paired points is not different between the proximal-posterior, epicondyle, and distal-anterior femoral insertions. These variations were statistically different during IR90° for the 3 different femoral locations. In increasing degrees of flexion, there was a length decrease between paired points observed with the proximal-posterior position. A length increase was observed for both the epicondyle location and the distal-anterior location.ConclusionsThe ALL did not reveal an isometric behavior at any of the femoral insertion locations but had different length change patterns during knee flexion and internal tibial rotation at 90°. The proximal and posterior to epicondyle femoral position is the only position with a favorable isometry, as shown by being tight in extension and in internal rotation at 20° and then relaxed when the knee goes to flexion at 120° and during internal rotation at 90°.Clinical RelevanceClinical relevance is significant with respect to optimizing the femoral position of an ALL reconstruction.