The causes of rattling of cheek bones when opening mouth may include trauma, dysfunction of masticatory muscles, temporomandibular joint disorder syndrome, and so on. 1. Trauma: due to traumatic stimulation caused by temporomandibular joint injury, resulting in joint capsule, joint head damage and the cheek bone rattling when opening the mouth, which may be accompanied by pain and swelling at the same time. Patients should avoid external stimulation, local braking, and reduce the activities at the cheek. 2. Dysfunction of masticatory muscle group: due to poor chewing habits or external impact, etc. caused by temporomandibular joint strain, resulting in dysfunction of masticatory muscle group and the symptoms of rattling of cheek bones. 3. Temporomandibular joint disorder syndrome: Temporomandibular joint disorder syndrome is caused by sudden biting of hard objects or sudden opening of the mouth, which leads to pain or joint popping sound when opening and closing the mouth. If the symptom of rattling of cheek bones when opening the mouth persists without relief, timely diagnosis and treatment should be carried out to avoid delaying the condition.