Standing knee US versus knee MRI for evaluating medial meniscal extrusion

Introduction:A weight-bearing (WB) knee ultrasound (US) represents a conceptual shift from static morphological to functional assessment.This study aimed to compare the ability of magnetic resonance imaging (MRI), non-weight-bearing US (NWB-US), and WB-US for diagnosing medial meniscal extrusion and to determine the prevalence of minor and major extrusion grades.Material and methods: Findings were categorized as normal medial meniscus, minor, and major medial meniscal extrusion.Cochran's Q test and McNemar's test with Holm-Bonferroni correction were used for statistical analyses.Results: This study included 50 adult patients (14 women and 36 men, mean age 37.8 10.1 years) with knee pain.MRI classified more knees as normal (n = 40, 80.0%) compared to NWB-US (n = 20, 40.0%) and WB-US (n = 7, 14.0%) (p < 0.001).WB-US identified minor (n = 20, 40.0%) and major (n = 23, 46.0%, p < 0.001) medial meniscal extrusion more frequently.NWB-US identified 17 (34.0%)minor and 13 (26.0%)major cases.MRI identified 4 (8.0%) and 6 (12.0%) minor and major medial cases, respectively.There was a trend toward greater medial meniscal extrusion with increasing patient age across all three imaging methods.The effect of BMI depended on the imaging modality: extrusion frequency increased with MRI and WB-US as BMI increased, while medial meniscal extrusion decreased with increasing BMI in NWB-US.Conclusion: WB-US was more useful than MRI and NWB-US for diagnosing minor and major grades of medial meniscal extrusion.Increasing age was the most significant factor, with BMI affecting results depending on the imaging modality used.