The ACL originates from the medial and anterior aspect of the tibial plateau and runs superiorly, laterally, and posteriorly toward its insertion on the lateral femoral condyle. The ACL is composed of the anteriomedial and posteriolateral bundles. Together, these bundles provide approximately 85% of total restraining force of anterior translation. It also prevents excessive tibial medial and lateral rotation, as well as varus and valgus stresses. To a lesser degree, the ACL checks extension and hyperextension. Together with the posterior cruciate ligament (PCL), the ACL guides the instantaneous center of rotation of the knee, therefore controlling joint kinematics [ 19, 21 ].
Muscles surrounding the knee joint further contribute to knee stabilization during lower extremity movements. Primary muscles include the quadriceps anteriorly, hamstrings posteriorly, gluteus medius and tensor fascia lata/IT band laterally and the hip adductors medially. The repetitive, eccentric nature of muscular activity about the knee during sports may lead to fatigue related injuries [ 10 ].