There are several possibilities for a knee to squat, stand up, or go up and down stairs: 1. The synovial membrane is enlarged, and the confined space of the knee is under negative pressure. The normal meniscus is crescent-shaped, but most children with a ringing sound have a disc-shaped meniscus, which is called a disc-shaped meniscus. Because of the abnormal development of the disc-shaped meniscus, in addition to its disc-like shape, it is often thicker and more prone to injury and tearing than the normal meniscus, causing children to cry out for knee pain after going up and down stairs, climbing, or squatting and standing. Parents who do not know the cause often ignore that each pain is actually a further aggravation of the injury. An early and correct diagnosis can be made arthroscopically to repair the abnormal meniscus to a normal shape. The most effective test for diagnosis is MRI MRI. In children who have developed to a basic level of maturity, the remaining portion in early treatment is often not very damaged and has a normal texture, and repair sutures can be considered. If the child cannot be seen in time and waits until the pain is abnormally severe repeatedly, the meniscus is most likely completely removed and cannot be preserved. The technology of meniscus transplantation in China is not yet mature, and only few hospitals have carried out this technology. Therefore, parents should pay attention to their children’s knee pain so that they do not miss the best time to treat it and lose their meniscus at a very young age.