The posterior horn of the medial meniscus is located at the posterior edge of the medial knee, adjacent to the posterior cruciate ligament, and this area is the most prone to injury. The medial meniscus is C-shaped, and the lateral meniscus is O-shaped. Most of the meniscus in China has this structure, and the chance of injury to the medial meniscus is higher in China. After meniscus injury, the diagnosis can be made clearly by MRI or arthroscopy, and certain treatment can be given to prevent the wear and tear of the knee cartilage after meniscus injury, which can cause secondary osteoarthritis.