Abstract
PURPOSE: To elucidate the relationship between medial meniscus extrusion (MME) and meniscal tear type in osteoarthritic knees. It was hypothesised that the type of meniscal tears in osteoarthritic knees would be relevant factors in triggering MME. METHODS: Patients with medial compartmental knee osteoarthritis were retrospectively reviewed. MME was defined as the distance from the extruding edge of the meniscus to a line drawn perpendicularly from the medial edge of the tibial plateau. Meniscal tears were classified into four types on magnetic resonance imaging: horizontal tear, medial meniscus posterior root tear (MMPRT), small radial tear and radial tear combined with a complex tear. A multivariate logistic regression analysis was performed to identify risk factors associated with pathological MME. RESULTS: A total of 153 patients with 58 ± 8 years were included. The averages amount of MME values were 3.4 ± 1.9 mm for horizontal tears (n = 42), 5.0 ± 1.3 mm for MMPRTs (n = 25), 4.2 ± 2.0 mm for small radial tears (n = 20) and 5.0 ± 2.2 mm for large/complex radial tears (n = 66). The amount of MME for MMPRTs and radial tear combined with complex tear was significantly greater than that of horizontal tears (p = 0.001, p < 0.0001, respectively). In multivariable analysis, age, MMPRT and radial tear combined with complex tear were identified as significant risk factors associated with MME greater than 3 mm (p = 0.006, 0.003 and 0.013; odds ratio = 1.09, 10.70 and 3.03, respectively). CONCLUSIONS: The presence of a radial tear combined with a complex tear was significantly correlated with MME, similar to MMPRT. This finding indicates that radial tears, which extend in multiple directions, may increase the risk of MME. Therefore, radial tears warrant careful evaluation, as they may carry a risk of MME comparable to that of MMPRTs. LEVEL OF EVIDENCE: Ⅳ, retrospective case study.