Patterns of Associated Knee Ligament and Chondral Injuries in First-Time Traumatic Patellar Dislocation: A Retrospective Magnetic Resonance Imaging (MRI) -Based Study.

Introduction First-time acute traumatic patellar dislocation, when managed without a knee magnetic resonance imaging (MRI) scan, may lead to missed diagnoses of important associated knee injuries. The aim of this study was to ascertain the incidence of associated ligamentous and cartilaginous injuries in first-time traumatic patella dislocation. Methods  This was a five-year retrospective study on patients aged 16-45 who had knee MRI scans showing the characteristic bone bruise patterns seen in traumatic lateral patellar dislocation. Anonymized data from the hospital picture archiving and communication system (PACS) was obtained with each scan reviewed by a consultant radiologist, a fellowship-trained orthopaedic knee specialist, and an orthopaedic registrar or resident. Results  A total of 200 knee MRI scans were screened. 61 eligible knee MRI scans were included in the study. The patients' ages ranged from 16 to 42 years old, with a mean of 25 years. 73.8% were male. A medial patellofemoral ligament (MPFL) tear or rupture occurred in 58 of 61 knees (95%) with MPFL attenuation in three (5%) injured knees. Meniscal injuries were identified in 5 of 61 knees (8.2%), medial collateral ligament (MCL) injuries in 11 of 61 knees (18%), osteochondral injuries and loose bodies in 17 of 61 knees (27.9%), and anterior cruciate ligament (ACL) injury in one knee (1.6%). Conclusions  This single-centre MRI-based study has provided information on the incidence of associated chondral and ligamentous injuries in patients with first-time acute traumatic patellar dislocation. This information will be useful for clinicians when counselling patients and will add to the available literature on this injury. An MRI scan should be obtained in cases of suspected first-time traumatic patellar dislocations, especially in active young patients, due to the incidence of other associated traumatic knee lesions that might need surgical treatment and lead to persisting knee symptoms if neglected.