Introduction An injury to the anterior cruciate ligament (ACL) is considered one of the most serious knee injuries in football, leading to the most time lost from competition. The study aimed to investigate the ACL injury mechanism in football across a cohort of elite and recreational players. Materials and Methods This registry-based study identified patients from the Danish National Patient Register (DNPR) with ICD codes S835 (cruciate ligament lesion) and M235 (chronic knee instability) from 2000-2018. Participants completed a questionnaire on ACL injury mechanism, and only players injured while playing football were included. Results A total of 90,608 patients were identified in the DNPR. This study investigates the 8,253 reporting an ACL injury while playing football. Most ACL injuries (52.9%) were non-contact, with 26.7% occurring during acceleration and pivoting. Physical contact with another player accounted for 47.1% of injuries. More players reported contact with another part of the body (23.7%) than direct contact on the injured knee (17.4%), and 73.5% of these physical contact-injuries resulted from a tackle. Female players were significantly more likely to sustain ACL injuries as goalkeepers (p=0.007) and right forwards (p<0.001), whereas male players were more frequently injured as central midfielders (p<0.001). Conclusion The most common ACL injury mechanism identified in this study was non-contact pivoting movements, followed by indirect physical contact with a body part other than the injured knee. Female players were significantly more likely to sustain ACL injuries as goalkeepers and right forwards, whereas male players were more frequently injured as central midfielders.
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