The knee rattles when squatting, mainly due to the following reasons: 1, the knee is within the meniscus and ligaments and other structures, when the body squatting, the femur, tibia and meniscus squeeze, will trigger a sound, this is a normal phenomenon. 2, may be the meniscus injury and osteoarthritis, the patient squatting will appear when the knee has a sound. If this causes the knee to rattle, it will be accompanied by pain and other uncomfortable symptoms. 3, may be due to the lack of calcium in the body, local lubricating fluid production is less, induced by the knee rattle. When this happens, patients are advised to take appropriate calcium supplements. If the pain occurs, the patient should go to the hospital to see what the cause is, and then give targeted treatment.