Many people look at an MRI report and see a description of “1st degree meniscus damage” or “2nd degree meniscus damage”, but is the “damage” described in the MRI report a true meniscus tear? Is this a true meniscal tear? Meniscus signal: Meniscus degree 1 signal: MRI shows spherical high signal, which indicates mucocutaneous degeneration and degeneration of meniscus tissue, and the patient has no symptoms and no clinical significance (Figure 1-1). Figure 1-1, the spherical high signal in the meniscus indicated by the arrow is the degree 1 signal. Meniscus degree 2 signal: MRI shows a linear high signal with horizontal alignment, which is a continuation of degree 1 signal, and the patient has no clinical symptoms. Figure 1-2, the arrow pointing to a linear high signal in the meniscus with a horizontal pathway is a degree 2 signal Meniscal degree 3 signal: MRI shows a high signal image leading to at least one of the upper and lower surfaces of the meniscus, indicating a true meniscal tear (Figure 1-3). Sagittal contrast with the corresponding area in coronal view helps to discriminate between 2nd and 3rd degree signals. In Figure 1-3, the high signal indicated by the arrow through the lower surface of the meniscus is a tear. The left 1-3 images show a horizontal meniscal tear, while the right image shows a meniscal tear combined with a meniscal cyst. Diagnostic points and easy mistakes: (1) The 1st and 2nd degree signals are degeneration within the meniscal parenchyma, not a tear. (2) A 3-degree signal indicates a meniscal tear. (3) A 3rd degree signal is defined as a tear leading to the superior or inferior surface of the meniscus. (4) In addition to the 3rd degree signal, the morphology (size and shape) of the meniscus can also be used to interpret meniscal injury.