Factors associated with medial meniscal extrusion in non-osteoarthritic knees with medial meniscus tears: A cross-sectional study.

Background: Medial meniscal extrusion (MME) plays an important role in the progression of knee osteoarthritis. Exploring the factors associated with MME in non-osteoarthritic knees may assist in the prevention of osteoarthritis.

Objective: To identify the factors associated with pathologic MME in non-osteoarthritic knees with medial meniscus tears (MMTs).

Design: A cross-sectional study.

Participants: One hundred fifty patients with non-osteoarthritic knees who underwent arthroscopic surgery for MMT. Patients were divided into a pathologic MME group (n = 54) and a control group (n = 96) based on whether a pathologic MME was present on magnetic resonance (MR) images.

Setting: Tertiary medical institution.

Interventions: Not applicable.

Main Outcome Measures: The MME distance was measured on a coronal MR image obtained at the midpoint of the medial femoral condyle. An MME distance ≥3 mm was considered to indicate pathologic MME. Demographic and clinical data were collected as variables. Multivariable logistic regression analysis was performed to identify factors associated with pathologic MME.

Results: After multivariable adjustment, body mass index (BMI) and the type of MMT were associated significantly with pathologic MME in the multivariable logistic regression model. Each unit higher in BMI was associated with a 13% higher risk of pathologic MME (odds ratio [OR] 1.13, 95% confidence interval [CI] 1.01-1.28, p = .04). The odds of pathologic MME were approximately four times and three times higher for radial tears (OR 4.34, 95% CI 1.25-15.03, p = .02) and complex tears (OR 3.07, 95% CI 1.17-8.05, p = .02) than for horizontal and longitudinal tears.

Conclusions: BMI and the type of MMT were independent factors associated with pathologic MME in non-osteoarthritic knees with MMT. A higher BMI, radial tears, and complex tears were predisposed to pathologic MME.