Continued Sex-Differences in the Rate and Severity of Knee Injuries among NCAA Soccer Players, 2004-2009

BACKGROUND: Studies continue to report a greater risk of knee injury in female, compared with male athletes; however, there are no comparable data on injury severity. PURPOSE: We extend previous analyses and examined sex-differences in the rate and severity (lost days of participation, need for surgery) of knee injuries among collegiate soccer players between 2004 and 2009, while controlling for several covariables previously linked to injury occurrence. METHODS: Data from the National Collegiate Athletic Association Injury Surveillance System (NCAA-ISS) were used to calculate injury incidence density (ID) per 1000 athletic exposures (AE). As per the data collection guidelines of the surveillance system, injury incidence was defined as: 1) any injury event involving the knee that occurred during participation in an intercollegiate game or practice; 2) that required medical attention and/or surgery; and 3) restricted participation or performance for \u3e 1 day beyond the event. The rate ratio (RR), along with the 95% Wald confidence interval (CI), compared incidence density among female, relative to male soccer players (the referent group). Multivariable regression and multivariable negative binomial regression modeling then tested the relation between sex and knee injury incidence and severity among all injured soccer players, while controlling for contact, setting, and division level, as well as for the interactions among these variables. RESULTS: Between 2004 and 2009, the sex-specific rate of knee injuries was 1.20 per 1000 AEs in women and 0.90 per 1000 AEs in men [RR =1.45, 95% CI = (1.27, 1.64)]. In the multivariable modeling, women continued to experience significantly higher odds of knee injury compared with men [aOR =1.44, 95% CI = (1.27, 1.63)]. Also, the adjusted odds of a knee injury that resulted in surgery remained higher in women compared with men [aOR = 1.61, 95% CI= (1.00, 2.58)]. From the negative binomial modeling, we observed that women also experienced significantly more lost time from participation, independent of contact, competition level, and surgery (beta=0.129; p=0.05). CONCLUSION: Given the prominence of soccer play in the United States, continued efforts to evaluate and improve knee injury prevention practices and policies may be especially important for female players