title: The Effects of Level of Competition, Sport, and Sex on the Incidence of First-Time Noncontact Anterior Cruciate Ligament Injury.
abstract: BACKGROUND
  Anterior cruciate ligament (ACL) injuries are disabling and are associated with the early onset of posttraumatic osteoarthritis. Little is known regarding the incidence rate of first-time noncontact ACL injuries sustained during athletic events and how they are independently influenced by level of competition, type of sport, and the participant's sex.
  
  
  OBJECTIVE
  Level of competition (college or high school), type of sport (soccer, basketball, lacrosse, field hockey, football, rugby, volleyball), and the athlete's sex independently influence the incidence rate of first-time noncontact ACL injuries.
  
  
  METHODS
  Cohort study; Level of evidence, 2.
  
  
  METHODS
  Between fall 2008 and spring 2012, first-time noncontact ACL injury data were collected from 8 colleges and 18 high schools across 7 sports. Athlete exposure was computed retrospectively using team rosters and numbers of scheduled practices and games. Injury incidence rates (IRs) were computed per 1000 athlete exposures. The independent effects of level of competition, sport, and sex on ACL injury risk were estimated by Poisson regression.
  
  
  RESULTS
  Colleges reported 48 ACL injuries with 320,719 athlete exposures across all sports studied (IR = 0.150 per 1000 person-days), while high schools reported 53 injuries with 873,057 athlete exposures (IR = 0.061). After adjustment for differences in sport and sex, college athletes had a significantly higher injury risk than did high school athletes (adjusted relative risk [RR], 2.38; 95% CI, 1.55-3.54). The overall IR for female athletes was 0.112 compared with 0.063 for males. After adjustment for sport and level of play, females were more than twice as likely to have a first-time ACL injury compared with males (RR, 2.10; 95% CI, 1.34-3.27). With lacrosse as the reference group, risk of first-time noncontact ACL injury was significantly higher for soccer players (RR, 1.77) and for rugby players (RR, 2.23), independent of level of play and sex.
  
  
  CONCLUSIONS
  An athlete's risk of having a first-time noncontact ACL injury is independently influenced by level of competition, the participant's sex, and type of sport, and there are no interactions between their effects. Female college athletes have the highest risk of having a first-time noncontact ACL injury among the groups studied.
authors.affiliation: McClure Musculoskeletal Research Center, Department of Orthopaedics and Rehabilitation, University of Vermont College of Medicine, Burlington, VT, USA bruce.beynnon@uvm.edu.
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Beynnon
authors.affiliation: Department of Medical Biostatistics, University of Vermont, Burlington, VT, USA.
authors.forename: Pamela M
authors.initials: PM
authors.lastname: Vacek
authors.affiliation: McClure Musculoskeletal Research Center, Department of Orthopaedics and Rehabilitation, University of Vermont College of Medicine, Burlington, VT, USA.
authors.forename: Maira K
authors.initials: MK
authors.lastname: Newell
authors.affiliation: McClure Musculoskeletal Research Center, Department of Orthopaedics and Rehabilitation, University of Vermont College of Medicine, Burlington, VT, USA.
authors.forename: Timothy W
authors.initials: TW
authors.lastname: Tourville
authors.affiliation: McClure Musculoskeletal Research Center, Department of Orthopaedics and Rehabilitation, University of Vermont College of Medicine, Burlington, VT, USA.
authors.forename: Helen C
authors.initials: HC
authors.lastname: Smith
authors.affiliation: Department of Kinesiology, University of North Carolina at Greensboro, Greensboro, NC, USA.
authors.forename: Sandra J
authors.initials: SJ
authors.lastname: Shultz
authors.affiliation: McClure Musculoskeletal Research Center, Department of Orthopaedics and Rehabilitation, University of Vermont College of Medicine, Burlington, VT, USA.
authors.forename: James R
authors.initials: JR
authors.lastname: Slauterbeck
authors.affiliation: McClure Musculoskeletal Research Center, Department of Orthopaedics and Rehabilitation, University of Vermont College of Medicine, Burlington, VT, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Johnson
mesh_terms: D000293:Adolescent; D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries; D056352:Athletes; D001265:Athletic Injuries / Q000453:epidemiology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D007718:Knee Injuries / Q000453:epidemiology*; D008297:Male; D012574:Schools; D012737:Sex Factors; D017695:Soft Tissue Injuries / Q000453:epidemiology; D013334:Students; D055815:Young Adult
keywords: ACL; anterior cruciate ligament; epidemiology; first-time; incidence; injury; noncontact; rate