The knee popping without pain is considered to be physiological popping, meniscus injury, knee osteoarthritis and so on. 1. Physiological popping: if the knee area remains static for a long time, when suddenly doing flexion, extension and pulling movements, physiological popping will occur, which is mainly in the exercise, the synovial fluid in the synovial fluid gas will form tiny bubbles, bubbles rupture after the ringing. 2. Meniscus injury: most of the meniscus injuries are related to knee sprains, especially in elderly patients, the meniscus will have degenerative diseases, the elasticity will be weakened, the slightest external force will cause meniscus injuries, and some patients will have a tearing sensation and popping sound in acute injuries, and a ringing sound will be heard during activities. 3. Knee arthritis: knee arthritis is a degenerative knee cartilage and osteophytes as the characteristics of the disease, articular cartilage can reduce the friction between the joints, but the cartilage has been damaged, in the activities of the popping symptoms, in the early stages of the disease may not be particularly obvious pain. In the early stage of the disease, the pain may not be particularly obvious. There may be other reasons for knee popping, so it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or standardized treatment.