LOS ANGELES (February 2005)—As women's participation in sports has skyrocketed, so have women's sports injuries. That is why researchers at the University of Southern California are launching a study to understand why female athletes are prone to knee-joint trouble—and how to prevent it.

The $1.2 million, National Institutes of Health-sponsored study will specifically look at sports-associated movements that make the anterior cruciate ligament, or ACL, so vulnerable to tears in athletic women. To better understand the basis of this high ACL-injury risk, researchers from the USC Division of Biokinesiology and Physical Therapy will study 240 youth and adult soccer players in the Los Angeles area.

“Studies have shown that women in certain sports suffer ACL injuries at a rate three to eight times greater than their male counterparts,” says Christopher M. Powers, Ph.D., P.T., associate professor at USC and the study's principal investigator. Soccer players may face an especially high risk: An analysis of collegiate soccer players during the early 1990s found that 31 percent of women had an ACL injury, compared to only 13 percent of men.

“To prevent these injuries, we need to better understand how these injuries occur and potential risk factors,” he says. “Surprisingly, little is known about women's sport-specific movement patterns and how they may contribute to knee injury.”

The ACL is the primary stabilizer of the knee and prevents the joint from rotating or extending too far. Because of the rapid stops and twists involved in soccer, and the forces involved with these movements, many female soccer players are far too familiar with the sudden popping sensation and knee instability brought on by an ACL tear.

First, Powers and colleagues will evaluate soccer-specific activities to see how those movement patterns vary between males and females. Researchers will recruit 80 male and 80 female participants between ages 9 and 24 from club teams and recreational leagues. Testing will take place at USC's Musculoskeletal Biomechanics Research Laboratory.

Participants will wear reflective markers on key points on their feet, legs and hips during various soccer-related exercises (such as cutting and jumping to head a ball), An eight-camera motion analysis system will track the markers' locations to analyze movement patterns. In addition, electrodes placed on the skin will provide information on muscles' electrical activity.

Researchers also will compare differences in movement patterns among pre-teen, teen-age, young adult and adult participants. By doing so, Powers and colleagues hope to determine at what age potentially harmful patterns appear so that adequate prevention strategies can be applied at the right time to prevent a future knee injury.

In the second part of the study, investigators will evaluate the influence of an ACL injury prevention program developed by the Santa Monica Orthopaedic Group in Santa Monica , Calif. This training program has been shown to successfully decrease the incidence of ACL injuries in female soccer players, and the USC researchers seek to learn why. “If we can understand how these training programs change injury-causing movement patterns, then perhaps more efficient and effective injury prevention programs can be developed,” says Powers.

In the second part of the study, 180 healthy female soccer players between ages 12 and 24 will undergo the same movement analysis at USC as previous participants. However, half of them will participate in a 10-week-long, injury-prevention exercise program which will be implemented by Competitive Athlete Training Zone (CATZ) trainers. At the end of the study, the females who participated in the training program will be compared to the females who did not participate in the training program to see if movement patterns have changed, and researchers will examine if such changes are suggestive of a decreased risk for ACL injury.

To learn more or to determine study eligibility, please call (323) 442-2454.