Reducing gender bias in anterior cruciate ligament injury research

September 26, 2008

Much has been learned about characteristic sex differences in knee structure and function, but researchers still know little about the underlying causes of the differences or whether they reflect an increased injury risk for physically active women versus men, according to a new consensus statement on anterior cruciate ligament (ACL) injuries from the National Athletic Trainers' Association (NATA).

Much has been learned about characteristic sex differences in knee structure and function, but researchers still know little about the underlying causes of the differences or whether they reflect an increased injury risk for physically active women versus men, according to a new consensus statement on anterior cruciate ligament (ACL) injuries from the National Athletic Trainers' Association (NATA). The statement, "ACL Injuries: The Gender Bias Research Retreat IV," recommends that researchers take sex differences into account when they study ACL injuries because the factors associated with ACL injury risk may not be the same in women and men.

The latest research findings about ACL injuries in women and men include the following:

• ACL strain is related to the load and timing of ground reaction forces.
• ACLs in women differ slightly from those in men; women typically display a more upright posture when they contact the ground.
• Trunk and upper body mechanics influence factors in the lower extremities and in the ACL, as do hip position and stiffness.
• Fatigue increases ACL injuries.

Studies have shown key neuromuscular and biomechanical, anatomical and structural, and hormonal differences in men and women, according to the researchers. Examining those factors within each sex separately will be important for determining the specific role they may play.

For example, the researchers determined that the chances of a woman experiencing an ACL injury are not evenly distributed across the duration of the menstrual cycle but instead are greater during the preovulatory phase of the cycle. The ACL's mechanical and molecular properties probably are influenced by not only estrogen but also the interaction of several sex hormones, secondary messengers, remodeling proteins, and mechanical stresses, they noted, adding that the interactive effect of all relevant hormones on ACL injury risk must be studied in more detail.

The consensus statement also addressed the need for risk factor screening and prevention efforts. Training programs that incorporate elements of balance training, plyometric training, education, strengthening, and feedback may alter the variables thought to contribute to ACL injuries, the researchers noted, although the protective effect of ACL injury prevention training programs appears to be transient. While work is done to identify the risk factors for ACL injury, the statement recommended continuation of controlled studies for evaluating the ability of prevention strategies to alter risk factors and prevent ACL injuries.

This statement is the result of a fourth research retreat focused on gender bias in ACL injuries. Leading researchers in musculoskeletal health attended. The consensus statement was published in September in the Journal of Athletic Training, NATA's scientific publication.

To review the entire "ACL Injuries: The Gender Bias Research Retreat" consensus statement, visit http://www.nata.org/jat/jat_docs/
08consensus_statement. pdf. For more information on the NATA, visit its Web site at www.nata.org. Or, contact the organization at National Athletic Trainers' Association, 2952 Stemmons Freeway, Dallas,TX 75247; telephone: 214-637-6282; fax: 214-637-2206.