An Overview of Clinically Relevant Biomechanics of the Anterolateral Structures of the Knee

Residual anterolateral rotatory laxity following injury and reconstruction of the anterior cruciate ligament (ACL) has become a popular topic and has generated interest in characterizing the relative contribution from the anterolateral structures of the knee. Studies have reported on the anatomic and biomechanical features of the anterolateral ligament (ALL), revealing a role in restraining internal tibial rotation in both ACL-intact and ACL-deficient knees. The Kaplan fibers of the iliotibial band have also been reported to provide significant restraint to internal tibial rotation. The ACL is the primary restraint to anterior tibial translation, and both the proximal and distal bundles of the iliotibial band, with a divergent orientation, also provide significant static restraint against internal tibial rotation, and each bundle may have a distinct individual role. In the setting of ACL deficiency, subsequent sectioning of the ALL and Kaplan fibers led to further increases in anterior tibial translation. Residual rotatory laxity that may be seen clinically following ACL reconstruction may be attributable to an associated anterolateral structure injury even in the setting of an anatomic ACLR, leading to consideration for a concomitant anterolateral structure reconstruction. Studies evaluating the kinematic influence of anatomic ALL reconstruction or lateral extra-articular tenodesis have focused on internal rotation, axial plane translation, and anterior tibial translation, with variable results having been reported. Further, despite the long history of anterolateral structure reconstruction, most commonly with a lateral extra-articular tenodesis, the clinical use of these combined techniques is still in its relative infancy, and long-term patient outcomes have yet to be published for relative comparisons.