by Joseph F. Wilcox, M.D.

Each year in the United States approximately one in 100 female high school athletes will suffer a serious, season-ending knee injury.

Even more distressing, depending on the sport, the incidence of anterior cruciate ligament (ACL) injuries in female athletes is two to ten times higher than in male athletes of the same age.

Sports with the greatest risk are basketball, soccer, volleyball, gymnastics and skiing, but these injuries are seen in any sport that involves cutting, jumping, landing and/or pivoting. ACL injuries are an extremely traumatic event in a young woman's life, usually causing the loss of an entire season, starting position, and possibly even a scholarship (not to mention the necessity of an ACL reconstruction followed by six months or more of extensive rehabilitation). It has been estimated that in the Midwest, on average, parents spend $6000 per child on fees for sports such as club teams, personal training, camps, clinics, etc., and that the cost of the ACL injury itself including reconstruction and rehabilitation is approximately $17,000. Not surprisingly then, coupled with the large increase in participation by female athletes in high-risk sports over the past few years, there has grown a strong interest in the possible prevention of ACL tears in female athletes.

To explain the gender difference in ACL injuries, researchers first had to understand the difference in the forces that are exerted on the male versus the female knee during athletics. This has led to several theories over the years including differences in the size of the femoral notch, lower extremity malalignment in females (higher Q angles), and even the possible effect of hormones on ligamentous laxity. A popular theory was the difference in training between boys and girls through their adolescent years with regard to skill level, balance, coordination, strength and muscle recruitment.

In Cincinnati, Timothy Hewett, PhD, studied several videos sent from surgeons and coaches showing the exact moment that athletes (male and female) suffered ACL tears. He then compared these to other videos of female basketball players performing similar movements (foot plants, pivots, etc.) without tearing their ACLs. Using analyses with computer software, they concluded that the young women who had suffered ACL tears exhibited more trunk and upper body movement than either the men or the uninjured women, and this placed much greater pressure on the planted knee, finally collapsing it inward as it overloaded the ACL. Dr. Hewett goes on to say, "Our research suggests that the issue in injured female athletes is a lack of high-level ability to control deceleration and acceleration at the center of their mass in 3-dimensional space." To put it more simply, female athletes who injure their ACLs do not know how to adequately steady their upper bodies as they move. Prepubescent athletes, whether male or female, tend to move alike. However as maturing girls grow taller, they add comparatively little strength (unlike boys). In essence, once a girl reaches puberty, her center of mass moves higher, adding weight but not the power to control it. This combination is a set-up for a significant knee injury.

Gender-specific exercise programs that target strength and balance deficiencies have been set up in recent years in the hope that they will reduce female athletes' risk of ACL injury. Many researchers believe they can lower the risk until they are almost comparable to that of male athletes of the same age. One such program is the SportsmetricsTM gender-specific ACL injury prevention program developed by Frank Noyes, MD, of Cincinnati, Ohio. His program has been scientifically proven to reduce the incidence of female knee injuries through a rigorous plyometric training program. It encompasses not only ACL prevention but also performance enhancement techniques. They use jumping drills to teach the female athlete to preposition the entire body safely when accelerating (jumping) or decelerating (landing). These exercises are designed for neuromuscular retraining and proceed from simple jumping drills to multidirectional, sports-type movements. This instills a foundation of strength, coordination, and overall physical conditioning in the female athlete, and can be tailored to a sports-specific program. The program lasts for several weeks, meeting multiple times every week. Each session is approximately 1-1/2 hours long and includes a dynamic warmup, a plyometrics session, a speed and agility session, a high-intensity strength-training session, and finally an emphasis on flexibility training as well. There are also less intensive programs for athletes who do not have the ability to train for that amount of time.

The Cardinal Orthopaedic Institute currently has physical therapists specializing in sports medicine who are also certified in the SportsmetricsTM injury prevention program.