Discoid menisci in children: MR features

To define the MR appearance of discoid meniscus in children.

In 22 children (15 girls and 7 boys; age range 5-17 years; median age 9 years) who were referred for evaluation of painful knees 27 discoid lateral menisci were identified. Meniscal shape and signal intensity and abnormalities of the surrounding structures were evaluated and compared with adult standards. Clinical (11 knees) or surgical (10 knees) follow-up was available on 16 patients (21 knees).

The menisci were classified as slab type (no. 20) or wedge type (no. 7). Transverse diameter at the midbody was 22.4 mm (range 10.5-36.7 mm) for discoid lateral menisci and 6 mm (range 5.1-28.3 mm) for medial menisci. Of 27 menisci, 23 had a central band of diffusely increased signal. Extension of intrameniscal signal to the joint space was noted in 16 of 23 menisci. Of 9 patients with intrameniscal signal who underwent surgery, only 7 had tears. Associated popliteal cysts occurred in 3 knees. No medial meniscal injury was observed.

The characteristic MRI appearance of symptomatic discoid meniscus in children is that of a diffusely thick meniscus with a slab configuration and diffusely increased intrameniscal signal that may or may not extend to the joint surface.