Correlation between medial meniscus degenerative tears and medial meniscus extrusion and dynamics using ultrasonography.

Abstract

Evaluating the correlation between degenerative meniscus tears and medial meniscus extrusion is necessary to determine the appropriate treatment plan for early-stage knee osteoarthritis. This study evaluated the relationship between degenerative meniscal tears and medial meniscus extrusion in early-stage knee osteoarthritis by using ultrasonography. A total of 132 knees from 123 patients with early-stage knee osteoarthritis were evaluated retrospectively. Medial meniscus extrusion at knee flexion angles of 0° and 90°, and meniscal degenerative tears, were evaluated using ultrasonography and magnetic resonance imaging. Medial meniscus extrusion was classified into four grades, while degenerative meniscal tears were categorized into five types as follows: type 0, no tear or only degenerative changes; type 1, horizontal tear only in the posterior segment of the medial meniscus; type 2, horizontal tear shown in both the posterior and middle segments of the medial meniscus; type 3, flap tear or maceration of the medial meniscus; type 4, medial meniscus posterior root tear or radial tear. Correlations between the type of meniscal tear and the medial meniscus extrusion grade in each meniscal tear group were evaluated. The meniscal tear type was significantly correlated with the medial meniscus extrusion grade (r = 0.518, p = 0.001). The percentages of cases with medial meniscus extrusion grade 2 or 3 (i.e., medial meniscus extrusion >3 mm at knee flexion angle of 0°) were 23.8 %, 50.0 %, 86.8 %, 94.1 %, and 92.3 % for types 0-4, respectively. The percentages of cases with medial meniscus extrusion >3 mm at knee flexion angles of 0° and 90° were 0 %, 20.0 %, 52.6 %, 70.6 %, and 50.0 % for types 0-4, respectively. The more severe the meniscal degenerative tear, the greater the medial meniscus extrusion and the more abnormal the dynamics in early-stage knee osteoarthritis.