@article {Patel873, author = {Akash D Patel and Garrett S Bullock and Jordan Wrigley and Mark V Paterno and Timothy C Sell and Justin M Losciale}, title = {Does sex affect second ACL injury risk? A systematic review with meta-analysis}, volume = {55}, number = {15}, pages = {873--882}, year = {2021}, doi = {10.1136/bjsports-2020-103408}, publisher = {British Association of Sport and Excercise Medicine}, abstract = {Objective To determine sex-based differences in risk of a second ACL injury (overall and by laterality) following primary ACL reconstruction in athletes who are attempting to return to sport.Design Systematic review with meta-analysis.Data sources Systematic search of five databases conducted in August 2019.Eligibility criteria for selecting studies Studies reporting sex-based differences in the incidence of second ACL injury in athletes attempting to return-to-sports and who were followed for at least 1 year following primary ACL reconstruction.Results Nineteen studies were included in this review, with seven studies excluded from the primary meta-analysis due to high risk of bias. The remaining 12 studies (n=1431 females, n=1513 males) underwent meta-analysis, with all 19 studies included in a sensitivity analysis. Total second ACL injury risk was 21.9\% (females: 22.8\%, males: 20.3\%). Females were found to have 10.7\% risk of an ipsilateral ACL injury and 11.8\% risk of a contralateral ACL injury. Males were found to have 12.0\% risk of an ipsilateral ACL injury and 8.7\% risk of a contralateral ACL injury. No statistically significant differences were observed for total second ACL injury risk (risk difference=-0.6\%, 95\% CI -4.9 to 3.7, p=0.783, I2=41\%) or contralateral ACL injury risk (risk difference=1.9\%, 95\% CI -0.5\% to 4.4\%, p=0.113, I2=15\%) between sexes. Females were found to have a 3.4\% absolute risk reduction in subsequent ipsilateral ACL injury risk compared with males (risk difference=-3.4\%, 95\% CI -6.7\% to -0.02\%, p=0.037, I2=35\%).Conclusion Both sexes have \>20\% increased risk of experiencing a second ACL injury. Any difference in the absolute risk of either a subsequent ipsilateral or contralateral ACL injury between sexes appears to be small.Registration PROSPERO (CRD42020148369)}, issn = {0306-3674}, URL = {https://bjsm.bmj.com/content/55/15/873}, eprint = {https://bjsm.bmj.com/content/55/15/873.full.pdf}, journal = {British Journal of Sports Medicine} }