When yawning, the cheek bone crunching generally refers to the temporomandibular joint popping, caused by temporomandibular joint popping for many reasons, the common ones are temporomandibular joint disorder syndrome, temporomandibular joint osteophytes, trauma, and so on. 1. Temporomandibular joint disorder syndrome: cold stimulation or long-term unilateral chewing of food can lead to excessive flexion and extension of masticatory muscles, resulting in temporomandibular joint disorders, leading to cheek bone rattling when yawning and other mouth opening movements. 2. Temporomandibular joint osteophytes: degenerative changes in the temporomandibular joint can lead to temporomandibular joint osteophytes or bony encumbrances, which can also lead to temporomandibular joint rattling. 3. Trauma: caused by direct damage to the masticatory muscles or the capsule of the temporomandibular joint due to trauma. There may be other reasons for TMJ popping, if it occurs for a long time or accompanied by other discomforts, you should consult the doctor in time and standardize the treatment.