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Ligament Dominance
The increased risk of anterior cruciate ligament injury among female athletes is best predicted by the motion and loading of the knee during performance situations. The ligament dominance theory suggests that females typically perform athletic movements with greater knee valgus angles. A greater amount of stress is placed on the ACL in these situations because there is high activation of the quadriceps muscles despite limited knee flexion, limited hip flexion, greater hip adduction, and a large knee adductor moment. Additionally, females typically land with their tibia rotated internally or externally. As a result of increased knee valgus stress, ground reaction forces are greater and laterally directed.

Quadriceps Dominance
Ligament dominance is observed when there is excessive movement in the frontal plane to accommodate limited movement in the sagittal plane. This is caused by weakness in the hamstring muscles or reliance on the strength of the quadriceps muscles. This quadriceps dominance theory identifies when the hamstring muscles are notably weaker than the quadriceps muscles. As a result, knee stability in performance situations depends on the quadriceps due to a discrepancy in the pattern in recruiting quadriceps and hamstring muscles.

Trunk and Leg Dominance
Other theories used to explain the increased risk of ACL injury among female athletes include the trunk dominance and leg dominance theories. Trunk dominance suggests that males typically exhibit greater control of the trunk in performance situations as evidenced by greater activation of the internal oblique muscle. Leg dominance suggests that females exhibit greater kinematic leg asymmetry in knee valgus angles, hip abduction, and ankle abduction in performance situations.