title: A multisport epidemiologic comparison of anterior cruciate ligament injuries in high school athletics.
abstract: BACKGROUND
  The knee joint is the second most commonly injured body site after the ankle and the leading cause of sport-related surgeries. Knee injuries, especially of the anterior cruciate ligament (ACL), are among the most economically costly sport injuries, frequently requiring expensive surgery and rehabilitation.
  
  
  OBJECTIVE
  To investigate the epidemiology of ACL injuries among high school athletes by sport and sex.
  
  
  METHODS
  Descriptive epidemiology study.
  
  
  METHODS
  Using an Internet-based data-collection tool, Reporting Information Online (RIO), certified athletic trainers from 100 nationally representative US high schools reported athlete-exposure and injury data for athletes from 9 sports during the 2007/08-2011/12 academic years. The outcome of interest in this study was ACL injuries.
  
  
  RESULTS
  During the study period, 617 ACL injuries were reported during 9 452 180 athlete exposures (AEs), for an injury rate of 6.5 per 100 000 AEs. Nationally, in the 9 sports studied, an estimated 215 628 ACL injuries occurred during the study period. The injury rate was higher in competition (17.6) than practice (2.4; rate ratio [RR] = 7.3, 95% confidence interval [CI] = 6.08, 8.68). Girls' soccer had the highest injury rate (12.2) followed by boys' football (11.1), with boys' basketball (2.3) and boys' baseball (0.7) having the lowest rates. In sex-comparable sports, girls had a higher rate (8.9) than boys (2.6; RR = 3.4, 95% CI = 2.64, 4.47). Overall, 76.6% of ACL injuries resulted in surgery. The most common mechanisms of injury were player-to-player contact (42.8%) and no contact (37.9%).
  
  
  CONCLUSIONS
  Anterior cruciate ligament injury rates vary by sport, sex, and type of exposure. Recognizing such differences is important when evaluating the effectiveness of evidence-based, targeted prevention efforts.
authors.affiliation: Center for Injury Research and Policy, The Research Institute at Nationwide Children's Hospital, Columbus, OH.
authors.forename: Allan M
authors.initials: AM
authors.lastname: Joseph
authors.forename: Christy L
authors.initials: CL
authors.lastname: Collins
authors.forename: Natalie M
authors.initials: NM
authors.lastname: Henke
authors.forename: Ellen E
authors.initials: EE
authors.lastname: Yard
authors.forename: Sarah K
authors.initials: SK
authors.lastname: Fields
authors.forename: R Dawn
authors.initials: RD
authors.lastname: Comstock
mesh_terms: D000293:Adolescent; D016118:Anterior Cruciate Ligament / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D056352:Athletes; D001265:Athletic Injuries / Q000453:epidemiology*; D005260:Female; D006801:Humans; D007717:Knee / Q000601:surgery; D007718:Knee Injuries / Q000453:epidemiology* / Q000503:physiopathology / Q000601:surgery; D007719:Knee Joint / Q000601:surgery; D008297:Male; D012574:Schools; D012737:Sex Factors; D013177:Sports; D013334:Students