The anterior cruciate ligament (ACL) is an important contributor to knee joint stability during athletic maneuvers such as cutting to change directions. Approximately 70-80% of all ACL injuries are non-contact in nature and the injury rate is 2-8 times greater in females compared to males. This study measured quadriceps, hamstrings and gastrocnemii activation patterns and biomechanical features at the hip, knee and ankle in 21 male and 21 female adolescent soccer players while performing an unanticipated straight run, cross-cut and side-cut. It was hypothesized that differences between genders and medial-lateral muscle sites would be identified and related to non-contact ACL injury risk factors.

Kinematic differences during the stance phase of the maneuvers were captured at the hip and ankle, with the most notable gender difference being a reduced hip flexion angle in females for the 2 cutting maneuvers. Several joint moment differences were also identified, particularly during the first 20% of stance and at the hip. In comparison to females, males generated a greater hip flexion moment for all 3 maneuvers, suggesting that hip biomechanics may have a significant role towards to the gender bias of non contact ACL injuries.

Neuromuscular differences were captured for the entire stance phase, the 100 msec pre-contact phase and early (0-20%) stance phase. Rectus femoris and lateral gastrocnemius activity was greater in females for all 3 maneuvers. Females also had a medial-lateral gastrocnemii activation imbalance that was not present in males. Throughout stance and compared to males, females also demonstrated reduced hamstring activity during the cross-cut and straight run and increased vastus medialis and lateralis activity during the straight run. The combination of these gender differences and medial lateral imbalances could be placing the female ACL at greater risk of being injured. Pre contact differences in the magnitude and shape of the hamstring, gastrocnemii and rectus femoris activation patterns also suggest that females may be using different neuromuscular control strategies as they prepare to execute unanticipated cutting maneuvers.

The neuromuscular and biomechanical differences were related to non-contact ACL injury risk factors and some of these potentially modifiable features could help improve current ACL preventative training programs.