ACL Denmark: A nationwide register-questionnaire study from 2000 to 2018 reporting stable ACL incidence rates but rising rates of reconstruction

Purpose: To describe the epidemiology of adult anterior cruciate ligament (ACL) ruptures in Denmark from 2000 to 2018, focusing on: (1) overall ACL incidence rate (IR) per 100,000 inhabitants per year, (2) sports-specific ACL IR per 100,000 athletes per year and (3) ACL reconstruction (ACLR) IR per 100,000 inhabitants per year. Methods: This registry study utilized prospectively collected data from the Danish National Patient Registry (DNPR). Two ACL IRs were calculated: unadjusted IR based on registry data and adjusted IR corrected using patient self-reports to account for diagnostic misclassification. Sports-specific ACL IRs (2012–2018) were estimated by combining self-reported injury data with sports participation figures from the National Olympic Committee and Sports Confederation of Denmark. ACLR IRs were calculated using procedure codes from DNPR, with annual Danish population data as denominators. Results: Between 2000 and 2018, 90,608 patients were identified: 40,691 completed questionnaires. Overall adjusted ACL IR remained stable between 107/100,000 (confidence interval [CI]: 104–111) in 2000 and 106/100,000 (CI: 103–109) in 2018, increasing among females from 81/100,000 (CI: 78–85) to 90/100,000 (CI: 87–94) and decreasing among males from 134/100,000 (CI: 129–140) to 122/100,000 (CI: 117–127). ACLR IR rose from 36/100,000 (CI: 34–38) to 43/100,000 (CI: 41–45), with increases in both sexes, particularly among younger (18–25 years) and older (>45 years) adults. Football was the leading cause of ACL injury overall and in men; women had more injuries in skiing and handball. The highest sports-specific ACL IR was in female handball players, peaking at 2880/100,000 athletes in 2017. Females showed higher IRs in pivoting sports, while males had higher rates in gymnastics. Conclusions: While overall ACL IRs remained stable, an increase among females and a decline in males were found. ACLR rates have risen in both sexes. Female handball players had by far the highest ACL IR. Level of Evidence: Level II.