@article {Poulsen1454, author = {Erik Poulsen and Glaucia H Goncalves and Alessio Bricca and Ewa M Roos and Jonas B Thorlund and Carsten B Juhl}, title = {Knee osteoarthritis risk is increased 4-6 fold after knee injury {\textendash} a systematic review and meta-analysis}, volume = {53}, number = {23}, pages = {1454--1463}, year = {2019}, doi = {10.1136/bjsports-2018-100022}, publisher = {British Association of Sport and Excercise Medicine}, abstract = {Objective To estimate knee osteoarthritis (OA) risk following anterior cruciate ligament (ACL), meniscus or combined ACL and meniscus injury.Design Systematic review and meta-analysis.Data sources MEDLINE, Embase, SPORTDiscus, CINAHL and Web of Science until November 2018.Eligibility criteria for selecting studies Prospective or retrospective studies with at least 2-year follow-up including adults with ACL injury, meniscal injury or combined injuries. Knee OA was defined by radiographs or clinical diagnosis and compared with the contralateral knee or non-injured controls.Study appraisal and synthesis Risk of bias was assessed using the SIGN50 checklist. ORs for developing knee OA were estimated using random effects meta-analysis.Results 53 studies totalling \~{}1 million participants were included: 185 219 participants with ACL injury, mean age 28 years, 35\% females, 98\% surgically reconstructed; 83 267 participants with meniscal injury, mean age 38 years, 36\% females, 22\% confirmed meniscectomy and 73\% unknown; 725 362 participants with combined injury, mean age 31 years, 26\% females, 80\% treated surgically. The OR of developing knee OA were 4.2 (95\% CI 2.2 to 8.0; I2=92\%), 6.3 (95\% CI 3.8 to 10.5; I2=95\%) and 6.4 (95\% CI 4.9 to 8.3; I2=62\%) for patients with ACL injury, meniscal injury and combined injuries, respectively.Conclusion The odds of developing knee OA following ACL injury are approximately four times higher compared with a non-injured knee. A meniscal injury and a combined injury affecting both the ACL and meniscus are associated with six times higher odds compared with a non-injured knee. Large inconsistency (eg, study design, follow-up period and comparator) and few high-quality studies suggest that future studies may change these estimates.Clinical relevance Patients sustaining a major knee injury have a substantially increased risk of developing knee OA, highlighting the importance of knee injury prevention programmes and secondary prevention strategies to prevent or delay knee OA development.PROSPERO registration number CRD42015016900}, issn = {0306-3674}, URL = {https://bjsm.bmj.com/content/53/23/1454}, eprint = {https://bjsm.bmj.com/content/53/23/1454.full.pdf}, journal = {British Journal of Sports Medicine} }