Anterior Cruciate Ligament Concomitant Injuries and Rotatory Knee Instability

Rotatory knee instability occurs when the normal knee biomechanics are altered, and the knee is unable to withstand the peak loads encountered during sporting and pivoting activities. Primary and secondary knee stabilizers play a critical role in this process, including the anterior cruciate ligament (ACL), the anterolateral, anteromedial, posteromedial, and posterolateral ligaments, menisci, and bony alignment. The most common injury pattern, anterolateral rotatory knee instability in an ACL-deficient patient, will be discussed. Although anatomic ACL reconstruction is the gold standard to treat ACL injuries in young athletes, it may fail to restore normal rotatory knee stability, especially in the setting of concomitant injuries to the surrounding tissues. Restoration of rotatory knee stability requires a deep understanding of the anatomy to successfully recreate knee biomechanics and allow patients to return to their preinjury levels. A thorough history and physical exam are mandatory along with adequate imaging to successfully diagnose concomitant injuries in the setting of ACL injury and manage this complex problem.