Epidemiology of Patellofemoral Instability Injuries Among High School Athletes in the United States

Background: Patellofemoral instability injuries, including dislocations and subluxations, are relatively rare in the general population but are believed to be much more common in young athletic patient populations, such as high school athletes. In spite of the relatively high risk, the epidemiology of such injuries in this population has not been clearly elucidated. Purpose: To provide a comprehensive understanding of the epidemiology of patellofemoral instability injuries among high school athletes in the United States. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Data were obtained from the National High School Sports-Related Injury Surveillance System, High School RIO (Reporting Information Online), an Internet-based sports injury surveillance system. Athletic trainers from high schools across the country uploaded data regarding athlete exposures (defined as practice or game participation) and injuries across 22 sports from 2007-2008 through 2012-2013. Data were collected regarding athlete demographics, injury mechanism and details, practice versus competition, return to sport, and the need for surgery. Results: A total of 421 patellar instability (143 dislocations and 278 subluxations) injuries occurred during 21,556,515 athlete exposures (AEs) during the study period, for an overall injury rate of 1.95 per 100,000 AEs. The highest injury rates were noted in girls' gymnastics (6.19 per 100,000 AEs), boys' football (4.10), and boys' wrestling (3.45). The overall injury rate was significantly lower for girls than boys (1.66 and 2.15, respectively; rate ratio [RR], 0.77; 95% CI, 0.62-0.94). In contrast, among only the sex-comparable sports, the injury rate was higher for girls than boys (1.47 and 0.88, respectively; RR, 1.67; 95% CI, 1.19-2.34). The rate of injury was higher in competition (3.72) than practice (1.34) (RR, 2.78; 95% CI, 2.29-3.36). A no-contact injury mechanism was the most commonly reported mechanism (37.8% of injuries), followed by player-to-player contact (36.8%). When all contact subcategories are combined, the overall contact mechanism represents 59.3% of injuries. Return to play after a patellofemoral instability injury occurred within 3 weeks for 59.5% of athletes. Return to play in >3 weeks (16.0%) and loss of the remainder of the season (20.0%) were less common outcomes. Conclusion: Patellofemoral instability injury rates vary by sport, sex, and type of exposure (competition vs practice). A better understanding of such patterns of patellofemoral instability injury will help drive formulation of new injury prevention strategies and decrease the risk for patellofemoral instability injury among high school athletes.