Exploring Predictors of Primary ACL Injury Risk in Military Cadets: The Role of Lower Extremity Strength and Demographics.

Context: Anterior cruciate ligament (ACL) injuries are prevalent in active populations, posing significant health risks. Despite advancements in surgery and rehabilitation, effectively preventing long-term health complications remains a significant challenge, underscoring the critical importance of developing effective ACL injury prevention strategies. Existing research into the risk of ACL injuries, in relation to lower extremity strength and demographic factors, often presents conflicting findings. These studies are frequently limited by small sample sizes or a narrow focus on specific muscle groups.

Objective: To explore the association between lower extremity strength, as measured by maximum voluntary isometric contraction (MVIC), demographic factors, and the risk of ACL injuries in a large sample of military cadets.

Design: Prospective Cohort Study.

Setting: Military service academies.

Patients or other participants: A total of 2,187 female and 3,432 male military cadets were recruited from three US military service academies.

Intervention(s): Cadets underwent baseline testing in the summer prior to their freshman year. Testing included demographics and MVICs for six muscle groups including the quadriceps, hamstrings, gluteus maximus, gluteus medius, and hip internal and external rotators. Cadets were prospectively followed for primary ACL injury incidence, from date of enrollment to graduation from service academy.

Main outcome measure(s): Multivariable logistic regression analyses were conducted to examine the association between MVIC values and primary ACL injury risk while controlling for demographic factors.

Results: There were 101 (38 females, 63 males) cadets that went on to sustain a primary ACL injury within their time at the academy. The results of this study found that greater gluteus maximus strength (OR = 0.32; P = 0.007) was associated with a decreased risk of ACL injury in military cadets. Cadets matriculating with higher BMI (OR = 1.09, P = 0.01) was associated with an increased risk of primary ACL injury in military cadets. All other factors were not statistically significant for predicting primary ACL injury risk.

Conclusion: This study suggests that greater gluteus maximus strength may have a protective effect against prospective ACL injury. Conversely, higher BMI appears to be a risk factor for prospective ACL injury. These findings may have important implications for the identification of at-risk individuals for targeted ACL injury prevention programs in military cadet populations.