Medıal Menıscus Extrusion on MRI: a Crıtıcal Indıcator for Hıgh-Rısk Tears and Assocıated Intra-Artıcular Pathologıes

Objective: To evaluate the relationship between medial meniscus (MM) tear morphology and meniscal extrusion, and to determine whether extrusion can be used as
an indicator for identifying high-risk tears based on knee MRI findings.
Materials and Methods: This retrospective study included 183 knee examinations from 160 patients. MM pathologies were classified as degeneration, horizontaloblique
tear, radial tear at the root region, and complex tear. Lateral meniscal pathologies, chondromalacia, joint effusion, and anterior cruciate ligament (ACL) status
were recorded. Meniscal extrusion was measured on coronal proton-density–weighted images. Intergroup differences were analyzed using the chi-square and Kruskal–
Wallis tests. Receiver operating characteristic (ROC) analysis was performed to predict high-risk tears. A multivariate logistic regression model was used to investigate
independent predictors of extrusion ≥3 mm.
Results: Radial root tears and complex tears demonstrated significantly greater extrusion compared with other pathologies. Chondromalacia and joint effusion were
significantly more frequent in knees with extrusion ≥3 mm. ACL rupture was associated with both increased extrusion and complex MM tears. ROC analysis identified
a threshold value of 3.27 mm (clinically approximated as 3 mm) for discriminating high-risk tears (sensitivity 84.4%, specificity 70.2%, AUC 0.82). In the regression
analysis, low-risk and high-risk tear groups as well as chondromalacia were identified as independent predictors of pathological extrusion.
Conclusion: MM extrusion, particularly values ≥3 mm, is a strong radiological indicator of radial root and complex tears and reflects accompanying degenerative
changes. Quantitative assessment of extrusion may contribute to the early diagnosis of surgically significant meniscal tears.