With the development of medicine and the application of arthroscopic technology in clinical practice, most knee injuries and diseases now no longer require incision surgery and long recovery times. Doctors can use arthroscopy to look directly inside the knee joint to diagnose and treat your disease. The most common knee conditions that are suitable for arthroscopic surgery are the following: i. Meniscal injury: A person can sustain a meniscal injury from a fall, body twist or external impact. After a meniscus injury, you will often experience pain in the knee joint when walking, and sometimes you will have the sensation that the knee joint is “pinched” and you can only resume walking with a little movement. You may also experience pain in your thighs, walking up and down stairs, or squatting. Meniscus injuries usually do not heal on their own and require arthroscopic surgery to remove or repair the damage. Second, cruciate ligament rupture: people can also damage the ligament when they fall, twist their body, or have a traumatic knee injury. After a cruciate ligament injury, you will feel weakness (instability) in the knee joint when you walk, afraid to run fast and stop sharply, mostly accompanied by thigh muscle atrophy and thinning, painful going up and down stairs or squatting, etc. The cruciate ligament rupture cannot heal on its own and requires arthroscopic surgery to reconstruct this ligament if necessary. Patellofemoral disease: The patella (commonly known as the “kneecap”) is located in front of the knee joint. It mainly supports the body’s activities such as walking up and down stairs, squatting and standing up. Due to genetics, trauma, muscle atrophy and other reasons, the shape or position of the patella can be abnormal (mostly displaced to the outside), then you will feel knee pain when walking up and down stairs, squatting or standing up, but there is no significant discomfort when walking and running on a flat surface. Patellofemoral disease often requires arthroscopic surgery to reduce and relieve pain when walking up and down stairs, squatting or standing up. IV. Intra-articular free body of the knee joint (joint rat): often due to trauma or breakage of bone spurs in the joint and the formation of fragments that can wander is called free body. When the free body wanders to the middle of the joint, it will suddenly produce joint pain and locking, and joint movement will be significantly limited, and it will gradually recover after the free body leaves the joint space. The free body can be removed arthroscopically. V. Fibrodysplasia in the knee joint: When you go up and down stairs, squat or stand up, the knee joint becomes sore or tender, but walking and running on a flat surface is not limited. This is due to a thin film of fibrous tissue left over from congenital development at the edge between the kneecap and thigh, which is thickened and enlarged by trauma or inflammation, and is squeezed into the gap between the kneecap and thigh bone, causing pain and joint instability. Conservative treatment of this disease is not ideal, and removal of the band under arthroscopy can effectively relieve the pain. Chronic synovitis: The synovium is a membrane lining the knee joint, which is rich in nerves and blood vessels. Many causes can cause chronic synovitis. The main manifestation is joint swelling and discomfort and pain after rainy days or exertion. Removal of hyperplastic synovial tissue under arthroscopy can largely relieve the symptoms. Osteoarthritis of the knee: joint degeneration caused by age-related arthritis, post-traumatic arthritis, rheumatoid arthritis disease can cause damage to the cartilage on the surface of the knee. The main symptoms are joint pain when walking, limited movement, joint extension, or joint deformity such as O-leg, X-leg, etc. If there is mild to moderate cartilage damage, or if you are unable or unwilling to undergo joint replacement surgery, you may be able to remove the bone spurs, trim the joint surface, and remove the synovial membrane to relieve pain. Rheumatoid arthritis: Rheumatoid arthritis is a systemic immune disease. Due to the disruption of the immune system, it destroys its own synovial tissue, leading to synovitis and further erosion and destruction of joint cartilage, eventually forming rheumatoid arthritis. In the early stages of synovitis (before the cartilage is destroyed), synovial hyperplasia can be removed arthroscopically to slow down the rate of cartilage destruction and slow down the development of rheumatoid arthritis.