Objective To discuss the MRI diagnostic criteria, classification and lesion characteristics of medial discoid meniscus of the knee. Methods We retrospectively analyzed the clinical data of all patients who accepted MRI examination of knee from November 2009 to March 2015.Twenty-six of them (28 knees) with medial discoid meniscus were screened out.We measured and analyzed in all cases the ratio of the width of meniscus to that of tibial plateau on coronal slice, and the thickest thickness of the meniscus posterior horn on sagittal slice.All cases were divided into complete and incomplete type according to MRI findings, and then we compared the lesion rate of the two types of medial discoid meniscus. Results Twenty-eight cases were divided into complete type (n=16) and incomplete type (n=12);there were 17 cases of medial discoid meniscal tears, with a lesion rate of 60.7%.The ratio of the width of meniscus to that of tibial plateau on coronal slice was 0.29±0.06, and the thickest thickness of the meniscus posterior horn was (5.31±0.92) mm.The lesion rate of complete type was 81.2%, and 33.3% of the incomplete type.The lesion rate of the complete type was higher than that of the incomplete type, and the difference was statistically significant (P < 0.05). Conclusions Three MRI diagnostic criteria for medial discoid meniscus are 3 or more than 3 consecutive layers discoid meniscus "tie-like" change in sagittal slice, the ratio of the width of meniscus to that of tibial plateau≥0.20, and the thickest thickness of the meniscus posterior horn≥4.40 mm.Medial discoid meniscuses are divided into complete and incomplete type; the lesion rate of complete type of medial discoid meniscus is higher than that of the incomplete type.

Citation： LiDongming, DengKaihong. The MRI Classification and Lesion Characteristics of Medial Discoid Meniscus. West China Medical Journal, 2016, 31(12): 2008-2012. doi: 10.7507/1002-0179.201600550 Copy