Lower Extremity Musculoskeletal Injury Risk After Concussion Recovery in High School Athletes.

Context:   Although an association between concussion and musculoskeletal injury has been described in collegiate and professional athletes, no researchers have investigated an association in younger athletes.
Objective:   To determine if concussion in high school athletes increased the risk for lower extremity musculoskeletal injury after return to activity.
Design:   Observational cohort study.
Setting:   One hundred ninety-six high schools across 26 states.
Patients or Other Participants:   We used data from the National Athletic Treatment, Injury and Outcomes Network surveillance system. Athletic trainers provided information about sport-related concussions and musculoskeletal injuries in athletes in 27 sports, along with missed activity time due to these injuries.
Main Outcome Measure(s):   Three general estimating equations were modeled to predict the odds of sustaining (1) any lower extremity injury, (2) a time-loss lower extremity injury, or (3) a non-time-loss lower extremity injury after concussion. Predictors were the total number of previous injuries, number of previous concussions, number of previous lower extremity injuries, number of previous upper extremity injuries, and sport contact classification.
Results:   The initial dataset contained data from 18 216 athletes (females = 39%, n = 6887) and 46 217 injuries. Lower extremity injuries accounted for most injuries (56.3%), and concussions for 4.3% of total injuries. For every previous concussion, the odds of sustaining a subsequent time-loss lower extremity injury increased 34% (odds ratio [OR] = 1.34; 95% confidence interval [CI] = 1.13, 1.60). The number of previous concussions had no effect on the odds of sustaining any subsequent lower extremity injury (OR = 0.97; 95% CI = 0.89, 1.05) or a non-time-loss injury (OR = 1.01; 95% CI = 0.92, 1.10).
Conclusions:   Among high school athletes, concussion increased the odds of sustaining subsequent time-loss lower extremity injuries but not non-time-loss injuries. By definition, time-loss injuries may be considered more severe than non-time-loss injuries. The exact mechanism underlying the increased risk of lower extremity injury after concussion remains elusive and should be further explored in future research.