Abstract Purpose Medial meniscal (MM) tears and extrusion contribute to knee osteoarthritis (OA) progression. This study investigated the effects of MM tear type on the degree and site of extrusion using magnetic resonance imaging (MRI) to assist in clinical treatment decision‐making. Methods We analysed 115 knees (58.3% women; mean age 63 years). OA severity was assessed using Kellgren–Lawrence (K–L) classification: K–L 0–1 (Group E), K–L ≥ 2 (Group A). Extrusion was measured at 13 points from anterior to posterior horn at 15° intervals on MRI. Patients were categorized by MM tear type: no tear (EN), longitudinal (EL), horizontal (EH), complex (EC) and posterior root (ER) in Group E. In Group A, complex (AC) and posterior root (AR) tears were analysed. Data were analysed using analysis of variance (ANOVA). Results Extrusion was significantly greater in the middle segments of EH, EC and ER groups than EN, whereas no significant difference was observed in EL. Marked middle segment extrusion was observed in ER. In AC, extrusion was greater than EN from anterior to posterior, whereas in AR, extrusion was significantly greater in middle and posterior segments. Conclusion MM extrusion is influenced by the type of meniscal tear and the severity of OA. Complex and posterior root tears result in increased middle to posterior extrusion. Understanding the relationship between the different types of MM tears and extrusion patterns can aid early detection of high‐risk tears and guide treatment strategies to prevent OA progression. Level of Evidence Level IV.
Ichiba et al. (Thu,) studied this question.