Rattling of the upper and lower jaws when opening the mouth, called joint popping, is a symptom of temporomandibular joint disorder. The main cause is the reversible anterior displacement of the joint disc. As the disc moves forward, it impacts with the condyle when opening the mouth and then returns to its normal position, a process that occurs when the joint pops, and in some cases, both opening and closing the mouth. For joint popping without dysfunction, joint protection measures can be prescribed, avoiding biting hard objects, localized moist heat packs, or the use of bite plates to harmonize and eliminate the popping. In some cases, joint popping will further develop and disappear, and there is restriction of mouth opening, due to the anterior displacement of the reproducible articular disk, which gradually becomes the anterior displacement of the irreversible articular disk, and the articular disk can not be reset, and the popping will disappear.