The causes of knee ringing when squatting mainly include physiological ringing and pathological causes of the knee joint. 1. Physiological popping: there are joint cavity and joint fluid in the knee joint, the joint cavity is negative pressure, when squatting, the joint is pulled or flexed, the tension exceeds the negative pressure of the joint cavity when the cavity will appear, the surrounding gases rush into the joint cavity and vibrate with the joint fluid, which will emit a single, crisp sound, known as physiological popping. Physiological popping is a normal phenomenon. 2. Pathological causes of the knee joint: refers to the knee joint structure is damaged, lesions and structural abnormalities of the sound, common meniscus injury, ligament laxity, articular cartilage off, osteoarthritis, joint instability, etc., can occur friction, sound. Pathological rattling is often characterized by a low, continuous sound, with or without pain. Pathological rattling needs to be clearly identified and actively treated.