The morphology of the meniscus on both sides of the normal knee is slightly different, with the medial meniscus in the shape of an “O” and the lateral meniscus in the shape of a “C”, the medial meniscus is narrower at the front and wider at the back, with the posterior part thicker than the anterior part, and the lateral meniscus is relatively more consistent. Both menisci were attached to the tibial plateau, with hypertrophied edges and thinner edges nearer to the center. The medial meniscus is thinner and larger than the lateral meniscus, and attaches more closely to the surrounding joint capsule. Normal menisci show low signal in all sequences of MRI, and in sagittal plane imaging, both menisci show a “bow-tie” pattern at the edge of the joint, and at the middle level, the anterior and posterior corners of the menisci are separated from each other, showing a wedge shape with small tips opposite to each other, and the posterior corner of the medial meniscus is longer than the anterior corner, whereas the anterior and posterior corners of the lateral meniscus are roughly equal in length. The posterior horn of the medial meniscus is longer than the anterior horn while the anterior and posterior horns of the lateral meniscus are approximately equal. MRI can show different degrees of meniscal damage. Degenerative lesions or tears of the meniscus can be characterized by high signal in the meniscus. Meniscal tears are divided into vertical and horizontal types. The former is most common in young people, as the fluid in the joint fills the tear, and MRI shows increased signal intensity at the tear. Horizontal tears are most common in the elderly, where mucus-like degeneration occurs in the center of the meniscus, followed by the formation of a horizontal tear, which shows high signal intensity on MRI. The interior of the fibrous meniscus contains linear or globular areas of high signal, which indicate mucous changes and pathological changes of the meniscal tear. In addition to signal abnormalities, meniscal tears may also show morphologic abnormalities, such as: blunting of the meniscal cusp, displacement of meniscal fragments, and narrowing of the posterior horn of the meniscus so that the posterior horn is smaller than the anterior horn. Depending on the degree of injury, Stoller grades: Grade 0: normal. Grade I: Signal appears as an irregular or spherical high signal shadow. Grade II: Signal appears as linear high signal, neither of which extends to the hemisection. Grade III: Signal is linear or diffuse high signal and extends to the articular surface, i.e., meniscal tear. To minimize the false-positive rate, a high signal extending to the meniscal surface must be seen in both the coronal and sagittal planes to diagnose a tear.