Meniscus serves as an important cushioning structure for the human knee. We usually artificially categorize meniscus into anterior horn, body and posterior horn. Among them, there are some differences in their manifestations on MRI depending on the grade and degree of injury to the posterior horn of the meniscus. For example, in grade I, it is manifested as a point or slice of high signal in the normal triangular low signal of the meniscus, but this high signal does not reach the edge of the meniscus. If there are short strips of high signals that do not reach the edge of the meniscus, we call this a grade II meniscus. When there is a clear bar or irregular pattern of high signal that reaches the edge of the meniscus, either at the edge of the articular surface or at the edge of the joint cavity, we call this a grade III meniscus injury. In addition, when the meniscus is more severely torn, the torn fragment can curl and shift. Then this displacement can even overlap with the residual posterior horn, and on imaging, we can see a more abnormal, hypertrophied posterior horn of the meniscus. At this point we have to be alert to the fact that there is not a torn meniscal fragment superimposed on the residual meniscus. Thus the manifestation of posterior meniscus horn injury is also clearly observable on MRI.