Concussions Increase the Odds of Lower-Extremity Injuries in National Football League Players: Four-Year Review of Publicly Available Data

OBJECTIVE: To investigate the effect of multiple concussions on the risk of lower-extremity injuries in National Football League (NFL) players. METHODS: All active NFL players from September 2016 to January 2017 through September 2019 to January 2020 regular seasons were eligible for inclusion. All players who sustained multiple concussions during the study period were identified using publicly available data and included in the multiple concussion (MC) cohort. Players who sustained a single concussion (SC) as well as controls were age and position matched to the MC cohort using MEDCALC case-control. Lower-extremity injuries were then documented for the players included in all 3 cohorts. RESULTS: The odds of sustaining a lower-extremity injury were significantly greater in the MC as well as the SC cohort when compared with the no concussion (NC)-matched cohort (odds ratio 2.92, standard deviation [SD] 1.7-4.9) and 2.28 (SD 1.5-3.6), respectively. However, we found no significant difference in the odds of sustaining a lower-extremity injury when comparing the SC with the MC cohort (odds ratio 1.00, SD 0.7-1.3). The time to lower-extremity injury after return to play from a concussion was significantly shorter in the SC group when compared with the MC group, within 1 year following a concussion injury (P = .01). CONCLUSIONS: There was a significant increase in the odds of suffering a lower-extremity injury after return to play in NFL players exposed to SC or MC when compared with age- and position-matched controls who did not sustain a concussion within the study period. There was no significant difference in the odds of suffering a lower-extremity injury after return to play for NFL players exposed to MC when compared with players exposed to a SC during our study period. Our findings suggest a potential need for injury-prevention protocols following concussion injuries. LEVEL OF EVIDENCE: Level III, retrospective comparative prognostic trial.