Researchers at the University of Michigan (Ann Arbor) have performed a systematic review and meta-analysis on ways to prevent anterior cruciate ligament (ACL) injuries. This is important because so many of today's sports injuries affect the ACL. Players can be sidelined for months (sometimes longer). In fact, it is estimated that one-quarter of a million ACL injuries occur each year in the United States.

What can be done to prevent these injuries? That is the question posed by many health care and sports professionals. Using a combined systematic review (searching the literature for all studies on the topic) and performing a meta-analysis (combining data together from many studies) is a good way to "mine the data" so-to-speak. The results of this current study provide us with evidence-based recommendations.

Before looking at the specific recommendations, it's important to understand why these are so important. It's not just that so many people experience ACL injuries. The fact is that many of these injuries are accompanied by damage to the surrounding tissues as well.

The result is a weak knee that is at risk for future injuries and even the development of early arthritis. Preventing ACL injuries not only protects people from pain and suffering, it can also protect the pocket book for the individual and for society.

Presently, there is a wide range of risk factors that might contribute to ACL injuries. Addressing any of these factors that can be modified (changed) may provide some protection. For example, muscular strength, alignment, and flexibility are modifiable factors. The use of high-risk positions and/or techniques during sports play and lack of aerobic conditioning are additional modifiable factors that can be analyzed and modified.

Improving any one or all of these features may reduce the anatomic risk of ACL injuries. Age, genetics, and hormonal factors are nonmodifiable and may contribute to ACL injuries but cannot be changed to reduce the risk of knee injury.

Risk factors outside of the human body but still within our control are referred to as environmental factors. These include playing surface, use of footwear and/or braces, playing outside in bad weather.

For anyone interested in a details of the data collection and analysis from this study, the authors provided summary tables and descriptions of eligible studies included. The majority of evidence supported two directions for prevention of ACL injuries: neuromuscular re-education and educational interventions. It turns out that training programs to address the anatomic risk factors do, indeed, reduce the risk of ACL injuries by as much as 50 per cent.

Since the studies available did not analyze individual parts of training programs, this systematic review/meta-analysis was unable to pinpoint exactly which training interventions work the best. It does appear that more time spent in training and following the exercise programs carefully (compliance) provide a direct protective effect.

The authors of this study suggest future studies need to be more complete, of higher quality, and make comparisons between specific groups and specific prevention interventions. Comparing one treatment against no treatment is not as helpful in determining the best prevention approach as comparing one intervention to another.

Reference: Joel J. Gagnier, ND, MSc, PhD, et al. Interventions Designed to Prevent Anterior Cruciate Ligament Injuries in Adolescents and Adults. In The American Journal of Sports Medicine. August 2013. Vol. 41. No. 8. Pp. 1952-1962.