Prior Injury History Strongly Associated with Future Lower Extremity Injury

Results from recently published paper:

Kucera KL, Marshall SW, Wolf SH, Padua DA, Cameron K, Beutler AI. Association of Injury History and Incident Injury in Cadet Basic Military Training. Medicine & Science in Sport & Exercise, 2016 Jan 13 [Epub ahead of print]. DOI: 10.1249/MSS.0000000000000872.

usafaWhy did you do this study?

Non-fatal injuries are the leading cause of medical encounter in the armed services and were responsible for 1.14 million outpatient visits in 2006. All four major branches of the U.S. military (Army, Navy, Marine, and Air Force) have identified physical training as a major priority for prevention efforts. Given the nature of military, which involves substantial stress to the lower extremity during marching, running, and jumping, it is not surprising that lower extremity injuries continue to be the most common injuries in military training, specifically overuse and sprains and strains. The purpose of this study was to describe the role of injury history as a risk factor for lower extremity injury and musculoskeletal-related conditions during the 8 week basic training period among first-year military cadets.

What did you do and what did you find in this study?

The data for this analysis come from the JUMP-ACL (Joint Undertaking to Monitor and Prevent ACL Injury) study—a collaborative multi-site prospective cohort study of neuromuscular risk factors for anterior cruciate ligament (ACL) injury. The JUMP-ACL study included a total of four classes for each of the three military academies (Army, Navy, and Airforce) over the 2005-2008 time period. A total of 9,811 cadets volunteered to participate and completed the baseline questionnaire. The questionnaire included questions about personal characteristics including their physical activity level and any lower extremity injuries they experienced prior to entering the military academy. Medically treated lower extremity injuries and musculoskeletal conditions during cadet basic training (July-August) were obtained from the Defense Medical Surveillance System (DMSS).

During cadet basic training there were a total of 3,157 medically treated lower extremity injuries: 45.5% were acute and 54.5% musculoskeletal-related.  Most frequent types of acute lower extremity injuries were ankle and lower leg sprains/strains (38.7%) and unspecified sprains/strains (34.9%). Overuse injuries were the most frequent types of lower extremity musculoskeletal conditions (89.6%). The overall risk of incident medically treated lower extremity injury during the basic training period (approximately 8 weeks) was 23.2% (95% CI: 22.3%, 24.0%). Injury risk was greater for females (39.1%) compared to males (18.0%) for all lower extremity injuries (Fig 1).

KuceraFigure 1

Male and female cadets with a previous history of lower extremity injury were at increased risk for a medically treated lower extremity injury during basic training. Male cadets over 19 years of age and female cadets who attended prep academy were at increased risk. Playing three or more high school sports and higher distance running volume were associated with lower risk of lower extremity injury. Stronger effects were observed for specific injuries including the ankle, knee and hip and for more severe injuries that interrupted physical activity.

How do these findings impact the public?

Injury history upon entry into the academy was strongly associated with medically-treated lower extremity injuries during cadet basic training. These findings emphasize the importance of identifying previous injuries and determining whether there are any deficits that may put an individual at risk for further injury. If deficits are detected, corrective measures can then be taken. These results are useful for health providers and underscore the importance of screening and prevention efforts.