Factors associated with meniscal extrusion in knees with or at risk for osteoarthritis: the Multicenter Osteoarthritis study

Abstract

Purpose: To assess the associations of meniscal tears, knee mal-alignment, cartilage damage, knee effusion, and body mass index with meniscal extrusion.

Materials and methods: The Multicenter Osteoarthritis study is an observational study of individuals who have or are at risk for knee osteoarthritis (OA). The HIPAA-compliant protocol was approved by the institutional review boards of all participating centers, and written informed consent was obtained from all patients. All subjects with available baseline knee radiographs and magnetic resonance (MR) images were included. MR imaging assessment of meniscal morphologic characteristics, meniscal position, and cartilage morphologic characteristics with use of the Whole-Organ Magnetic Resonance Imaging Score system was performed by two musculoskeletal radiologists. Cross-sectional associations of severity of meniscal tears, knee malalignment, tibiofemoral cartilage damage, knee effusion, and body mass index with meniscal extrusion were assessed by using logistic regression, with multiadjustments when testing each predictor.

Results: A total of 1527 subjects (2131 knees; 2116 medial and 2106 lateral menisci) were included. Medially, meniscal tears, varus malalignment, and cartilage damage were associated with meniscal extrusion, with odds ratios (ORs) of 6.3 (95% confidence interval [CI]: 5.0, 8.0), 1.3 (95% CI: 1.1, 1.7), and 1.8 (95% CI: 1.4, 2.2), respectively. Laterally, meniscal tears, valgus malalignment, and cartilage damage were associated with meniscal extrusion, with ORs of 10.3 (95% CI: 7.1, 14.9), 2.2 (95% CI: 1.5, 3.2), and 2.0 (95% CI: 1.3, 2.9), respectively.

Conclusion: Meniscal tears are not the only factors associated with meniscal extrusion; other factors include knee malalignment and cartilage damage. Meniscal extrusion is probably an effect of the complex interactions among joint tissues and mechanical stresses involved in the OA process.

Figure 1:

Coronal STIR image used for the assessment of medial and lateral meniscal extrusion. The section of reference is the one where the medial tibial spine (arrow) is seen with its greatest volume. Vertical lines passing by the outer edge of medial (M) and lateral (L) tibial plateaus, excluding osteophytes, are used as reference to assess extrusion of the body of the meniscus. No extrusion is seen on this image (grade 0).

Figure 2:

Coronal STIR image shows a grade 2 extrusion of the body of the medial meniscus. A single horizontally oriented oblique tear is depicted in the body of the medial meniscus (arrow). Note areas of cartilage damage in the medial tibiofemoral compartment (arrowheads).Vertical line = reference line for measuring extrusion in the coronal plane.