Contact injury mechanism is independently associated with greater Anterior Cruciate Ligament Injury Severity Scale severity in patients undergoing primary anterior cruciate ligament reconstruction

PURPOSE: To determine whether injury mechanism and sport category were independently associated with overall structural injury severity after sport-related primary anterior cruciate ligament (ACL) rupture, as quantified by the Anterior Cruciate Ligament Injury Severity Scale (ACLISS). METHODS: This retrospective analysis of prospectively collected data included consecutive patients undergoing primary ACL reconstruction between November 2022 and November 2024. Eligible patients had sustained a complete primary ACL rupture during sport, undergone magnetic resonance imaging within 8 weeks of injury and had complete imaging and arthroscopic documentation. Injury mechanism was classified as contact or non-contact, and sports as pivoting-contact, pivoting-non-contact or non-pivoting. Associations with severity grade were assessed using proportional-odds ordinal logistic regression adjusted for age, sex, body mass index and injury-to-surgery interval. Models evaluated injury mechanism, sport category and both exposures simultaneously. The continuous score was examined in sensitivity analyses. RESULTS: Among 482 patients, 175 (36.3%) sustained contact injuries and 307 (63.7%) sustained non-contact injuries. Contact injuries had higher ACLISS mean scores than non-contact injuries (4.6 vs. 3.8; p < 0.001) and were more frequently classified in higher severity grades. In the fully adjusted model, contact injury remained independently associated with greater severity (odds ratio, 2.68; 95% confidence interval [CI], 1.68-4.27; p < 0.001), whereas sport category was no longer associated with severity. Adding injury mechanism improved model fit, whereas adding sport category to a model already containing injury mechanism did not. Continuous-score analysis confirmed the principal finding (adjusted mean difference, 0.60 points; 95% CI, 0.29-0.91; p < 0.001). CONCLUSION: Among patients undergoing primary ACL reconstruction after a sport-related ACL rupture, contact injury mechanism was independently associated with greater structural injury severity. This association persisted after adjustment for sport category, whereas the association with sport category was attenuated. Injury mechanism should therefore be documented when characterizing injury severity. LEVEL OF EVIDENCE: Level III.