Bones rattle when you open your mouth, which may be related to temporomandibular joint disorder or jaw fracture. 1. Temporomandibular joint disorder: it is not a separate disease, it is a group of diseases that involve temporomandibular joint and/or masticatory muscles, manifested by joint popping, pain, and limitation of mouth opening. Its cause is unknown, may be related to mental stress, exertion, dental trauma, joint weight bearing, etc. Suffering from temporomandibular joint disorders can be manifested as a bone rattling when you open your mouth. 2. Jaw bone fracture: when trauma occurs in the maxillofacial area, jaw bone fracture can occur, with the body of the mandible, the ascending branch and condylar fracture more common. After jaw fracture, the clinical manifestations include occlusal disorders, restricted mouth opening, pain and bone friction sound at the broken bone end, which can show the bone ringing and pain when you open your mouth. There may be other causes of bone ringing when you open your mouth, so you should consult the doctor in time, improve the examination, clarify the cause and diagnosis, and receive regular treatment under the guidance of a professional physician.