The bulge on the outside of the knee needs to be treated, common causes include rheumatoid arthritis, osteoarthritis and cysts caused by meniscus injuries, and commonly used treatments are medication and surgery. 1. Rheumatoid arthritis: Rheumatoid arthritis is an autoimmune disease, the main treatment is to use glucocorticosteroids, such as methylprednisolone, prednisone and so on. 2. Osteoarthritis: The main treatment for osteoarthritis is pain relief, and non-steroidal anti-inflammatory drugs, such as celecoxib, are usually used to reduce local inflammatory reactions and relieve pain, in addition to correcting deformities and improving the restoration of joint function. 3. Meniscus injury: meniscus injury to the lateral posterior horn, there can be localized cysts, if the meniscus injury is mild, the use of non-steroidal anti-inflammatory drugs for pain relief can be (such as celecoxib). If the meniscus is at a grade 3 injury and a meniscal tear occurs, arthroscopic suture surgery is required. The bulge on the outside of the knee can also be caused by other reasons, such as a tibial fracture, and it is recommended to consult a physician for a definitive diagnosis and treatment. All of the above medications should be used under the supervision of a physician.