MRI of the medial meniscus in patients over 40 years of age with osteoarthritic knees

MRI was performed for 171 medial menisci of 147 patients, ranging in age from 40 to 86 years (mean 66.6 years), who showed clinical signs in the medial compartment. We classified the MRI findings of the medial menisci using the modified grading system of Crues et al. (Radiology 1987;164:445–448) [

], and their grade 3B into three types based on the shape of the meniscus at the menisco-capsular junction as follows; a blunted change with intrameniscal signal as type 1, flattened and/or herniated as type 2, and a diffuse swelling on the joint surface sometimes obscure as if shredded as type 3. Their mean age was lower in grades 1 and 3A, and higher in grades 2 and 3B. Their mean clinical evaluation score according to the Japanese Orthopaedic Association was higher in grades 1 and 3A, and lower in grades 2 and 3B. In grade 3B, type 1 showed similar MRI findings and had similar patient background to those in grade 2. The MRI of the medial menisci in the osteoarthritic knee of those aged 40 years or more showed characteristic shapes, especially at the menisco-capsular junction, that were correlated to patient age and to the clinical severity of the osteoarthritis. We concluded that the MRI findings of the medial meniscus were usefully divided into six groups: groups 1–3 with clear edges and groups 4–6 with diffuse edges.