Prevention of acute knee injuries in adolescent female football players: cluster randomised controlled trial OPEN ACCESS

Objective To evaluate the effectiveness of neuromuscular training in reducing the rate of acute knee injury in adolescent female football players. Design Stratified cluster randomised controlled trial with clubs as the unit of randomisation. Setting 230 Swedish football clubs (121 in the intervention group, 109 in the control group) were followed for one season (2009, sevenmonths). Participants 4564 players aged 12-17 years (2479 in the intervention group, 2085 in the control group) completed the study. Intervention 15 minute neuromuscular warm-up programme (targeting core stability, balance, and proper knee alignment) to be carried out twice a week throughout the season. Main outcome measures 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. ConclusionsAneuromuscular 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. Trial registration Clinical trials NCT00894595. Introduction Football (soccer) is the most popular sport worldwide with around 265 million players, and the number of female players is growing rapidly. For example, more than three million young people play football in the United States alone, and almost half of them are female; and in 2006 around 83 000 female football players from the age of 12 years were registered in Sweden (population around 9million).Unfortunately, knee injuries are common, and severe injuries such as anterior cruciate ligament injury constitute a serious problem in terms of long absence from or termination of football and early osteoarthritis. In football, the rate of anterior cruciate ligament injury is more than twofold higher in female players than in male players, 10 and adolescent girls are especially at risk. 11 Several parallel group controlled studies, most targeting adolescents, have evaluated injury prevention strategies in female football players. Only two non-randomised studies in adolescent footballers showed significant reduction of acute knee injuries or non-contact anterior cruciate ligament injuries with neuromuscular warm-up programmes. However, most studies were not designed specifically to evaluate preventive effects on knee or anterior cruciate ligament injury as the primary outcome, and high quality randomised controlled trials targeting prevention of acute knee injuries or anterior cruciate ligament injuries are lacking. The main objective of our stratified cluster randomised controlled trial was to evaluate the effectiveness of a neuromuscular warm-up programme in reducing the rate of acute knee injury, particularly anterior cruciate ligament injury, in adolescent female football players. Our hypothesis was that the rates of anterior cruciate ligament injury and acute knee injury would be significantly reduced in the intervention group compared with the control group. Correspondence to: M Waldén [email protected] No commercial reuse: See rights and reprints http://www.bmj.com/permissions Subscribe: http://www.bmj.com/subscribe BMJ 2012;344:e3042 doi: 10.1136/bmj.e3042 (Published 3 May 2012) Page 1 of 11