LAUSR

ObjectiveTo determine the incidence and MRI characteristics of the spectrum of posterolateral corner (PLC) injuries occurring in association with anterior cruciate ligament (ACL) rupture.Materials and methodsWe carried out a level IV, retrospective case series study. All patients clinically diagnosed with an ACL rupture between July 2015 and June 2016 who underwent MRI of the knee were included in the study. In addition to standard MRI knee reporting, emphasis was placed on identifying injury to the PLC and a description of involvement of these structures by two musculoskeletal radiologists. Association with PLC involvement was sought with concomitant injuries using correlation analysis and logistic regression.ResultsOne hundred sixty-two patients with MRI following ACL rupture were evaluated. Thirty-two patients (19.7%) had an injury to at least one structure of the PLC, including the inferior popliteomeniscal fascicle (n = 28), arcuate ligament (n = 20), popliteus tendon (n = 20), superior popliteomeniscal fascicle (n = 18), lateral collateral ligament (n = 8), popliteofibular ligament (n = 7), biceps tendon (n = 4), iliotibial band (n = 3), and fabellofibular ligament (n = 1). Seventy-five percent of all patients with combined ACL and PLC injuries had bone contusions involving the lateral compartment of the knee. The presence of these contusions strongly correlated with superior popliteomeniscal fascicle lesions (p < 0.05). There was no correlation between injuries to other structures of the PLC and other intra-articular lesions.Conclusion Missed injuries of the PLC lead to considerable morbidity. The relevance of this study is to highlight that these injuries occur more frequently than previously described and that an appropriate index of suspicion, clinical examination, and MRI are all required to reduce the risk of missed diagnoses. The results of this study support previous suggestions that the rate of concomitant PLC injury in the ACL-deficient knee is under-reported. The rate of combined injuries in this series was 19.7%. The key message of this paper is that PLC injury is common in the presence of ACL injury and should be sought both clinically and radiologically.