If you are a young female athlete, parent or coach of an athlete, you may be aware that adolescent girls have a 4 to 8 time higher risk of sustaining a non-contact anterior cruciate ligament (ACL) injury than male athletes participating in the same sports. While reasons for this may vary, an article published in Contemporary Pediatrics suggests that this higher risk factor is related to a female athlete’s neuromuscular control of knee motion during athletic activities such as landing from a jump or quickly changing direction:
Current evidence suggests that the primary reason girls are at greater risk than boys for noncontact ACL injuries is that girls tend to have less neuromuscular control of knee motion during athletic maneuvers. In other words, girls tend to use their muscles differently than boys when landing from a jump or quickly changing direction. Biomechanical studies have identified 4 neuromuscular strategies that are more common in girls and that may lead to dynamic knee valgus, a position that places the ACL at a high risk of tearing.
(1) Girls tend to use their quadriceps muscles much more than their hamstrings. Kinetic and kinematic analyses have found that during a jump landing or quick change in direction, girls have reduced knee flexion, increased quadriceps activity, and decreased hamstring activity compared with boys. This “quadriceps dominant” strategy has been shown to increase both anterior tibial translation and strain on the ACL.30 Notably, ACL strain is significantly reduced when there is co-contraction of the hamstrings.4
(2) Girls tend to have 1 leg stronger than the other, whereas boys tend to have equal strength in both legs. Asymmetry in leg strength promotes asymmetric weight distribution between the feet upon landing, causing a shift of the body’s center of mass away from its base of support, a position associated with increased risk of ACL injury.31
(3) Girls tend to have less core strength and stability, which makes it more difficult for them to control their center of mass and prevent it from shifting away from the base of support.19
(4) Girls tend to rely on bones and ligaments to stop joint motion, rather than contracting their muscles to control joint position and absorb the landing forces.
To help prevent injuries such as torn ACLs, the Santa Monica Orthopaedic and Sports Medicine Research Foundation designed a program that incorporates warm-up, stretching, strengthening, and sport-specific agility exercises. That program, known as the Prevent Injury and Enhance Performance program, or PEP, was shown in a 2008 study to reduce risk of ACL injury among female collegiate soccer players. According to a Centers for Disease Control and Prevention press release on the study:
The study followed 61 women’s soccer teams with 1,435 players in Division I of the National Collegiate Athletic Association for a single season. Twenty-six teams were randomly assigned to use the program and 35 other teams served as a comparison group. Teams participating in the study came from many different regions, conferences and experienced a variety of competitive success.
Researchers noted that while the number of injuries reported in this study was small, the use of the PEP program was effective in reducing the risk of ACL injuries, and the program can be done during regular practice time and without special equipment.
Integrating an effective warm up and strengthening program into your physical activity is essential for preventing injury and improving performance. If you are troubled with knee pain or wish to speak with someone about exercises you can do to help prevent injury and promote better performance, please contact our office to schedule an appointment with one of our providers.