The treatment methods of left knee medial meniscus posterior horn injury include conservative treatment and surgery. 1. Conservative treatment: It is suitable for the mild injury of the posterior horn of the medial meniscus of the left knee, within the second degree of injury, it should be braked and rested, and if necessary, it should be immobilized with a brace, and it can be used to take non-steroidal drugs such as ibuprofen and celecoxib orally, which can play the role of anti-inflammatory and analgesic. 2. Surgery: If the injury of the posterior horn of the medial meniscus of the left knee is serious or more than three degrees, surgery is usually needed, such as meniscus suture surgery, meniscoplasty, etc. After the surgery, rehabilitation training will be carried out under the guidance of the doctor, so as to avoid adhesion of the joint. Left knee medial meniscus posterior horn injury should actively cooperate with the doctor for targeted treatment, the above medication should be strictly follow the doctor’s instructions, avoid self-medication.