There are two common causes of joint rattling: first, congenital joint developmental laxity, joint developmental laxity refers to joint capsule and ligament laxity inside and outside the joint, resulting in poor joint stability, the patient can usually complete the hyperextension movement, the amplitude of movement is larger than normal, due to the instability of the joint, the cartilage of the joint surface will happen to hit each other, resulting in rattling in the joint; second, intra-articular ligament rupture leads to Second, the joint stability decreases due to the rupture of intra-articular ligaments, such as the rupture of the anterior cruciate ligament of the knee joint, the stability of the knee joint decreases, the tibial plateau moves forward excessively relative to the femur, and the femoral condyle and the tibial plateau collide and cause a ringing sound, which shows that the ringing sound is usually related to joint instability.