Studies geared to enhancing ACL injury prevention efforts

Determining which components of the typical 90-minute anterior cruciate ligament (ACL) injury prevention program work best to reduce injuries is the focus of a new study at the University of Michigan Bone & Joint Injury Prevention & Rehabilitation Center. The researchers suggest that improved efforts in ACL injury prevention could result in improved osteoarthritis (OA) prevention, noting that close to 70% of ACL injuries lead to an early onset of painful OA.

In current ACL injury prevention programs, athletes train 3 times per week at 90 minutes per session, the researchers noted. They often see young athletes becoming overwhelmed with this extra training and discontinuing the programs because they involve too much work and cut into their practice time. With their study, the researchers are trying to identify a more efficient prevention program that young athletes and their coaches and parents will be more inclined to incorporate into a routine.

The study will measure joint movements and forces typically performed on an athletic field, such as landing on 1 leg and pivoting, in 120 female athletes aged 10 to 18 years. After pretesting, all participants will be placed in 1 of 4 six-week prevention training program groups: (1) core stability and balance, (2) plyometrics, (3) neuromuscular training, and (4) a control. After 6 weeks, the participants will return to the laboratory for comparison of the movements performed before and after the training program. The success of each individual program component in modifying otherwise hazardous landing maneuvers-such as landing with a knee too straight or knock-kneed-will be evaluated.

The researchers suggest that changing the way persons move and making them more aware of how they move will reduce the frequency of ACL injuries, equip them to participate in sports activities more safely, and even improve their performance. The center’s activities involve a collaborative effort among the university’s Medical School, College of Engineering, School of Kinesiology, and School of Public Health.

In another study, evaluation of the knee muscles of a noninjured female athlete with electromyography was found to be effective in determining whether she is at high risk for an ACL rupture. Researchers at the Institute of Sports Medicine Copenhagen and the Danish National Research Centre for the Working Environment noted that electromyographic (EMG) analysis may be used to evaluate neuromuscular activity in specific muscles during sport-specific movements. They used electromyography to screen 55 noninjured female athletes while they performed a standardized side-cutting maneuver that is used frequently during games and often results in noncontact ACL injuries.

Five of the athletes had lower EMG signals in the medial hamstring muscle on the back of their thigh and higher activity in their quadriceps muscle; they all experienced an ACL rupture later in the competitive season. With analysis of EMG signals in all participants, a high-risk zone was defined; 10 athletes were in the high-risk zone initially, including the 5 who subsequently had a noncontact ACL rupture.

The study is the first to define a specific muscle group activity that may predispose a female athlete to an ACL injury, the researchers noted. They suggested that further studies with a larger sample size are needed to standardize neuromuscular screening for determining which athletes are in the high-risk zone.