Meniscal injuries are common, and MR examinations are currently a more reliable method of examination. The extreme torque of the femur against the tibial plateau can easily damage the meniscus, and if there is damage to the surrounding connecting ligaments, this may be accompanied by severe pain and bleeding in the joint cavity. According to the literature, the diagnostic accuracy of MRI of meniscal tears is 80%-100%. This range of variability in accuracy is related to many factors such as the level of awareness of the radiologist, the experience of the arthroscopist, meniscal fibrosis, free body interference, MRI examination modality, and the fact that some specific tears are not easily diagnosed. MRI presentation: The normal meniscus on all sequences of imaging shows a homogeneous low signal structure. When the meniscus is degenerated and torn, the joint fluid penetrates into the degenerated and torn parts of the plate, water molecules collect on the demarcation layer, and the interaction between the macromolecules and water in the plate reduces the proton freedom, thus shortening the T1 and T2 relaxation time, which is highlighted by the elevated signal of T1WI and proton density images at the degenerated and torn parts, and the reduced signal of T2WI images, however, the gradient echo (FE) sequence of T2WI showed a slightly higher signal. For this reason, FE T2WI findings are more sensitive than SE T2WI to signal changes within the meniscus. The size and morphology of MRI high-signal shadows in the meniscus and whether they extend to the upper and lower edges of the meniscus are closely related to the pathologic changes in the meniscus, and are currently categorized using a three-level classification: (a) Class I MRI manifestations: These manifestations are common in athletes and normal volunteers and are usually not clinically significant. Histology shows limited early mucinous-like degeneration within the meniscus with light hematoxylin and eosin staining in the oligochondrocyte region. The nomenclature of mucinous, mucin-like and hyaline degeneration depends on the degree of stromal mucopolysaccharide accumulation. (ii) Grade II MRI presentation: Horizontal, slightly elevated signal lines appear within the plate, which may extend from the capsule margin of the meniscus straight to the free edge, but do not affect the articular margin. Grade II MRI shows a larger extent of mucinous-like degeneration of the meniscus than grade I. Although there are no obvious fissures visible to the naked eye, there are often microscopic fissures or the presence of fibrous breaks within the cell-free region. The middle crossing fiber bundle divides the meniscus into upper and lower halves, acting as a buffer, and is normally low-signal with the rest of the meniscus, thus not visualized by MRI; mucus-like degeneration of the meniscus occurs most easily or first in the middle crossing fiber area, and MRI shows a horizontal, slightly high signal line, which is characterized by not extending to the articular rim of the meniscus. (iii) Grade III MRI presentation: When the slightly high signal line within the plate involves the articular rim of the meniscus, it is both a grade III change. Fibrocartilage tears are present in almost all grade III MRI, with intra-plate tears in 5-6% of cases. Arthroscopy cannot detect such tears enclosed within the plate and can only be confirmed pathologically after surgical resection, which may be one of the reasons for the 6% false positives on MRI versus arthroscopic analysis. In another 5-6% false negative cases, the MRI misidentifies the meniscal rim as hairy and fibrotic as a tear. Grade III MRI presentation of the meniscus may be associated with morphologic changes, including changes in height and width and loss of triangular pattern. The posterior horn of the medial meniscus is often subjected to tremendous tibiofemoral pressure and torsion, and the posterior inferior edge of the meniscus grinds against the tibial plateau resulting in a tear, with the highest incidence of tears in this area, accounting for approximately 45%-69% of all sites of the medial and lateral meniscus. Repair of the tear is a combination of chondrocyte multiplication and synovial proliferation, however, synovial ingrowth into the tear often leads to acute and chronic pain, as well as secondary osteoarthritis, and synovial thickening around the diseased meniscus can often be significant and markedly reinforcing. If the vascularization of the capsule edge of the meniscus grows into the meniscal tear, enhancement MRI will show weak or moderate enhancement of the meniscus.