Table I.

Search strategy used in the study.

Search strategy items	Details
Searched databases	PubMed/MEDLINE, Scopus, ISI
Searched string	(“anterior cruciate ligament” OR ACL) AND (lesion OR tear OR rupture OR injury) AND (soccer OR football) AND risk
Inclusion criteria	P: Articles investigating anterior cruciate ligament injuries in football players competing at any level. I: None (only observational, non-interventional studies were synthesized). C: With non-injured football players. O: Strength of the association between a risk factor and anterior cruciate ligament injury. Primary articles
Exclusion criteria	P: Articles investigating athletes in general and for which data relative to football players only could not be extracted. I: Articles dealing with the impact/effectiveness of prevention programs or interventions. C: With other sport disciplines. O: Articles studying risk factors of knee injury not focusing on anterior cruciate ligament rupture or for which data specifically related to anterior cruciate ligament could not be extracted; articles investigating electromyography, electromechanics, biomechanics, kinetics and kinematics of anterior cruciate ligament in non-injured football players, linking the findings with putative mechanisms of ACL injury; articles investigating tests for predicting risk factors of anterior cruciate ligament injury in football players; articles focusing on treatment and management of anterior cruciate ligament in football players from a clinical/surgical standpoint; articles studying return to play after anterior cruciate ligament injury in football players. Review articles
Time filter	None set
Language filter	None set
Target journals	American Journal of Sports Medicine; British Journal of Sports Medicine