To evaluate the role of magnetic resonance(MR) imaging in the diagnosis of the discoid meniscus, the authors reviewed 31 cases of discoid menisci diagnosed by MR imaging among which 16 cases received arthroscopy. Using knee surface coil, sagittal
T1,
T2, & protein density images and coronal T1 weighted images were obtained with 18 cm FOV & 4mm/1 mm thickness/gap. A discoid meniscus was considered if three or more contiguous sagittal images demonstrated continuity of the meniscus between the
anterior
and posterior horns or the diameter of the mid-portion of the meniscus exceeded 15 mm on the coronal image. The authors also observed the associated abnormalities including tears of meniscus and ligament, meniscal cyst, and osteochondral defects.
All
discoid menisci were lateral menisci and torn discoid lateral menisci were present in 26 cases(83%). In two cases, tears of the contralateral medial meniscus were present. The tears of anterior and posterior cruciate ligaments, meniscal cyst, and
osteochondral defects were present in 4, 2, 4, and 5 cases respectively. All collateral ligaments were intact.
In conclusion MR imaging was useful for the detection of discoid meniscus and associated abnormalities.
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