In clinical practice, we often encounter soccer fans who sprain their knee while playing soccer, and they may be swollen and painful at the time. I could hear a “clicking” sound in the joint, accompanied by a painful sensation, and from time to time, the joint would somehow get stuck suddenly, causing unbearable pain and immobility. This is why people ask, “How can this happen when there is no fracture? This requires an examination by a specialized orthopedic joint surgeon. After a detailed physical examination and an MRI of the knee, it is possible that the meniscus of the knee is torn and arthroscopic surgery is required. The question again is, is it so serious to have surgery after a sprain and no fracture? Indeed, many people will not understand this. This is because there has always been a misconception that as long as there is no fracture, there is no major problem. In fact, our knee joint is not only made up of bone, but more importantly some soft tissues such as cartilage, ligaments and synovial membranes, which together with the bone tissues maintain the stability and daily activities of the whole knee joint. The meniscus is one of the most important components. The meniscus is a tough, crescent-shaped disc, two for each knee joint, on the inner and outer sides, that moves with the femur above or the tibia below depending on the movement of the knee joint, acting as a cushion to absorb shock, reduce contact stress and maintain joint stability. Meniscal tears are a very common type of sports injury, often caused by uncoordinated joint movement, such as kicking a soccer ball in the air or against the foot, or tripping and falling during running and other knee sprains, resulting in the meniscus getting stuck between the femur and tibia and causing a tear. If other conditions exist at the same time, such as long-term squatting labor, original ligament injury, or original discoid meniscus, it is more likely to cause a tear. Older people are also prone to tears due to degenerative aging of the meniscus. And these tears can be caused even without obvious trauma. The most common symptom of a meniscus tear is pain during walking or exercise. The pain can be on one side of the joint, or posteriorly, or it can occur when the joint is extended and flexed to a certain position. Many patients may experience a “clicking” sound in the joint when squatting or walking, often at a fixed angle. Sometimes the joint suddenly becomes stuck and immobile or the joint suddenly becomes weak, which affects the quality of life. More seriously, the torn meniscus can also pull the synovial tissue during joint movement, wear out the joint cartilage, cause chronic synovitis that is extremely difficult to cure, and accelerate joint degeneration, making arthritis appear earlier. Therefore, meniscal tears must be diagnosed and treated as early as possible. Because the meniscus does not appear in the X-ray film, the damage to the meniscus cannot be detected by X-ray examination, especially in the acute phase of the tear, the swelling and pain of the joint affect the physical examination and diagnosis of the doctor, so that the meniscal tear is often missed, losing the time for treatment and delaying the condition. The development of modern medicine allows us to use MRI for early diagnosis of meniscus tears. For some cases that are difficult to diagnose, arthroscopic techniques can also be used to perform minimally invasive examinations, further improving the accuracy of diagnosing meniscal tears. Treatment for meniscal tears is surgical or non-surgical. Tears that are small and located in the vascular zone can be treated with external fixation brakes such as casts and knee braces. All tears other than these require surgical treatment. Generally, most meniscal tears that cause symptoms require surgical treatment. In the past, when meniscus tears were found, they were often removed altogether, which provided temporary relief, but the loss of meniscus protection would lead to the development of arthritis in just a few years. Therefore, current surgeries use techniques such as partial meniscectomy or meniscal suturing to preserve as much normal meniscal tissue as possible and reduce the impact on joint function. The application of arthroscopic technology has reduced the trauma of the surgery to a minimum, allowing the patient to achieve the fastest possible recovery.