title: Prevention of acute knee injuries in adolescent female football players: cluster randomised controlled trial.
abstract: OBJECTIVE
  To evaluate the effectiveness of neuromuscular training in reducing the rate of acute knee injury in adolescent female football players.
  
  
  METHODS
  Stratified cluster randomised controlled trial with clubs as the unit of randomisation.
  
  
  METHODS
  230 Swedish football clubs (121 in the intervention group, 109 in the control group) were followed for one season (2009, seven months).
  
  
  METHODS
  4564 players aged 12-17 years (2479 in the intervention group, 2085 in the control group) completed the study.
  
  
  METHODS
  15 minute neuromuscular warm-up programme (targeting core stability, balance, and proper knee alignment) to be carried out twice a week throughout the season.
  
  
  METHODS
  The primary outcome was rate of anterior cruciate ligament injury; secondary outcomes were rates of severe knee injury (>4 weeks' absence) and any acute knee injury.
  
  
  RESULTS
  Seven players (0.28%) in the intervention group, and 14 (0.67%) in the control group had an anterior cruciate ligament injury. By Cox regression analysis according to intention to treat, a 64% reduction in the rate of anterior cruciate ligament injury was seen in the intervention group (rate ratio 0.36, 95% confidence interval 0.15 to 0.85). The absolute rate difference was -0.07 (95% confidence interval -0.13 to 0.001) per 1000 playing hours in favour of the intervention group. No significant rate reductions were seen for secondary outcomes.
  
  
  CONCLUSIONS
  A neuromuscular warm-up programme significantly reduced the rate of anterior cruciate ligament injury in adolescent female football players. However, the absolute rate difference did not reach statistical significance, possibly owing to the small number of events.
  
  
  BACKGROUND
  Clinical trials NCT00894595.
authors.affiliation: Division of Community Medicine, Department of Medical and Health Sciences, Linköping University, 581 83 Linköping, Sweden. markus.walden@telia.com
authors.forename: Markus
authors.initials: M
authors.lastname: Waldén
authors.forename: Isam
authors.initials: I
authors.lastname: Atroshi
authors.forename: Henrik
authors.initials: H
authors.lastname: Magnusson
authors.forename: Philippe
authors.initials: P
authors.lastname: Wagner
authors.forename: Martin
authors.initials: M
authors.lastname: Hägglund
mesh_terms: D000293:Adolescent; D000070598:Anterior Cruciate Ligament Injuries; D001265:Athletic Injuries / Q000517:prevention & control*; D002648:Child; D016000:Cluster Analysis; D015444:Exercise / Q000502:physiology; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D006801:Humans; D057194:Intention to Treat Analysis; D007718:Knee Injuries / Q000453:epidemiology / Q000517:prevention & control*; D017063:Outcome Assessment, Health Care / Q000706:statistics & numerical data*; D012044:Regression Analysis; D012727:Sex Characteristics; D017678:Sex Distribution; D012916:Soccer / Q000293:injuries*; D013548:Sweden / Q000453:epidemiology