Multiple Ankle Injuries Are Associated With an Increased Risk of Subsequent Concussion in National Football League Players

BACKGROUND: There is a gap in the literature regarding musculoskeletal risk factors for concussion within the National Football League (NFL), which is an avenue that must be explored to promote player safety given the high incidence of both injury types. This study aims to observe if ankle injuries are associated with an increased risk of subsequent concussion in NFL players. METHODS: The public online database ProFootballReference.com was used to identify ankle injuries and concussions in NFL players from the 2009-2010 to 2019-2020 seasons. Multivariable logistic regression for subsequent concussion and ankle injury was performed, adjusting for body mass index (BMI), age, and player position. For descriptive statistics, unpaired t tests with unequal variance were performed for continuous variables, including BMI and age. χ(2) testing was performed for categorical variables, including player position, and whether the position was offensive, defensive, or on special teams. RESULTS: Of the 5538 NFL players included in the study, 941 had an ankle injury, 633 had a concussion, and 240 had both an ankle injury and a subsequent concussion. The adjusted odds ratio (aOR) for concussion following a single ankle injury was 0.90 (95% CI 0.72-1.14, P = .387); however, the aOR for concussion following multiple ankle injuries was 2.87 (95% CI 1.23-6.75, P = .015). Special teams players had the lowest risk for concussion (aOR 0.17, 95% CI 0.069-0.36, P < .001) following ankle injury, and there was no significant difference in risk between offense and defense (aOR 0.91, 95% CI 0.77-1.08, P = .295). CONCLUSION: Multiple ankle injuries were associated with an increased risk of a subsequent concussion after adjusting for BMI; player position; and offense, defense, or special teams designation. These findings can inform injury prevention practices in the National Football League. LEVEL OF EVIDENCE: Level III, retrospective comparative study.