March 12, 2004

American Academy of Orthopaedic Surgeons News Release For more information, contact: Claudette Yasell 847-384-4035, yasell@aaos.org or 415-978-3527 Mindy Weinstein 847-384-4034, weinstein@aaos.org Boise State contact: Pat Pyke 208-426-1987, ppyke@boisestate.edu Finding a magic bullet: Can training reduce knee injuries in female athletes? San Francisco —Studies of sports injuries conducted over the past three decades have indicated that female athletes involved in jumping and cutting sports sustain non-contact injuries to the anterior cruciate ligament (NC-ACL) of the knee at rates far higher than their male counterparts engaged in the same sports. These injuries are devastating to individuals. Literature shows that ACL injuries are a major inducer of knee osteoarthritis, for example, which is likely to significantly affect the quality of one’s life. This injury and possible prevention strategies were discussed today at a panel briefing during the American Academy of Orthopaedic Surgeons 71st Annual Meeting. Risk of knee injury soars for female athletes ACL injuries are among the most common of all sports-related knee injuries and they affect the lives of more than 250,000 people in the United States each year — most of them women. “Female recreational athletes have a probability of NC-ACL injuries 7.3 times greater than that of male recreational athletes,” says Bing Yu, Ph.D., associate professor and director, Center for Human Movement Science at the University of North Carolina at Chapel Hill. New research was presented today with orthopaedic surgeon William E. Garrett, Jr., MD, Ph.D., and professor, Department of Surgery, Duke University Medical Center. This controlled laboratory study included 30 male and 30 female recreational athletes between 18 and 30 years of age. “The most important aspect of the findings in our study is that we provide evidence that altered movement patterns are responsible for the elevated risk for NC-ACL injuries in women,” says Yu. “Specifically, we found that people who land hard — with excessive movements at the knee joint in athletic tasks — are at higher risk for NC-ACL injuries.” Yu suggests that female athletes may prevent these injuries if they can learn to “land light, and minimize twisting, as well as left or right bending movements of the landing leg. “We hope our studies can provide a solid scientific basis for clinicians to develop strategies to prevent NC-ACL injuries,” says Yu. “The results of studies in this area can be directly applied to clinical practice to improve the quality of health care and reduce the costs.” Motivating teens to train According to Timothy E. Hewett, Ph.D., Cincinnati Children’s Hospital and the University of Cincinnati College of Medicine, sports programs commonly make use of various types of training for their athletes. Some of these programs have proven effective in preventing injury. It is difficult, however, to get athletes to train solely to prevent injury. Hewett and his colleagues initiated a study to examine the effects of a comprehensive neuromuscular training program on measures of performance and lower extremity biomechanics in female athletes. Hewett’s hypothesis was that significant improvements in measures of performance — specifically vertical jump, single leg hop distance, speed, bench press, and squat — would be demonstrated along with improved biomechanical measures related to injury risk in female athletes. Along with his colleagues, Hewett recruited 41 female basketball, soccer, and volleyball players, ages 13 to 17 years, from Cincinnati high schools. He developed exercises essentially intended to allow these young women to generate power and control force. An important focus of the training was teaching the girls to jump properly and land softly. Specifically, Hewett taught the girls to use their knee joints as hinges and to flex their knees when they land. He also taught them to roll their feet as they hit the ground. “If I jump down from the height of a foot, I can land with an average four to six times my body weight in force,” he says. “If I roll my foot, however, I can cut that force about 50 percent. The more force I have coming up through my foot, the higher the chance that I’m going to tear a knee ligament.” Hewett’s athletes trained three days a week. Each training session lasted 90 minutes, not including a warm-up period prior to the training and 15 minutes of stretching exercises afterwards. At the end of six weeks, the results were “amazing,” he says. The mean predicted squat and the bench press improved; the right and left single leg hop distance increased as did the double leg vertical jump. Further, trained females demonstrated significantly lower sprint times than prior to training, on average. The study also demonstrated significant desirable biomechanical changes during a landing maneuver following the training. In contrast, the control group demonstrated no significant increase in any of the above measured parameters. Finding the magic bullet Ronald P. Pfeiffer, Ed.D., LAT, ATC, along with orthopaedic surgeon Kevin G. Shea, MD, and their colleagues at the Center for Orthopaedic and Biomechanics Research (COBR) at Boise State University completed a study that centered solely on evaluating whether a knee ligament injury prevention program would decrease the incidence of NC-ACL injuries. Pfeiffer’s results differed dramatically from Hewett’s, however. Among the 1,439 teens in his study, a total of six NC-ACL injuries were reported — three in the intervention group and three in the control group — leading Pfeiffer to conclude that his program had virtually no effect in preventing injuries. Pfeiffer’s study was essentially built around the premise that girls do not land correctly, or run and change directions correctly relative to their body position, when they are engaged in a sport. The sport metrics program he and his colleagues developed included numerous repetitive jumping and landing drills divided into 15- to 20-minute sessions, two to three times a week. “It could be that the program we developed is not sufficient in magnitude,” Pfeiffer speculates. Another reason that the training program did not reduce injury may be related to the age of the athletes – it may be necessary to start these training programs in younger athletes to reduce the risk of serious knee injury. “If exercise programs can be designed to reduce knee injuries in female athletes, they will be better accepted if they require a reasonable amount of training time, such as 20 to 30 minutes, two to three times per week. If we can’t come up with something that’s going to work in that length of time, then we may have to come up with a completely different approach to this problem. The bottom line, though, is that if intervention is the way to go with this injury, we need to come up with a magic bullet — whatever program that is.” According to Pfeiffer, the Centers for Disease Control and Prevention has criticized the sweep of studies on intervention completed over the past few years indicating that while all show promise, they suffered from multiple flaws. “We think it is time to do a rigorously implemented national collaborative study that includes not 1,400 athletes — but maybe 14,000.” Peiffer says that gathering statistically significant statistics is critical. An orthopaedic surgeon is a physician with extensive training in the diagnosis and non-surgical as well as surgical treatment of the musculoskeletal system, including bones, joints, ligaments, tendons, muscles and nerves. The 27,156-member American Academy of Orthopaedic Surgeons (www.aaos.org or http://orthoinfo.aaos.org) is a not-for-profit organization that provides education programs for orthopaedic surgeons, allied health professionals, and the public. An advocate for improved patient care, the Academy is participating in the Bone and Joint Decade (www.usbjd.org ) the global initiative in the years 2002-2011 to raise awareness of musculoskeletal health, stimulate research, and improve people’s quality of life. President Bush has declared the years 2002-2011 National Bone and Joint Decade in support of these objectives. The Academy’s Annual Meeting is being held March 10-14, 2004, at the Moscone Center in San Francisco, Calif.