When we open our eyes from the second, our mouth has entered into a busy work mode. Yawn, say good morning to our family, brush our teeth, eat, talk about work …… No matter work, study, or all activities in life need us to do the action of opening our mouths. Therefore, when we can’t open our mouths normally because of mouth opening pain, our quality of life will be greatly reduced, and we may even become anxious and restless. So is TMJ to blame for the painful opening of the mouth? TMJ disorders are a general term for a group of disorders that involve the temporomandibular joint and/or the masticatory muscle system. Painful opening of the mouth is one of the main clinical manifestations of TMJ disorders and is often the main reason why patients visit the hospital. To fully open the mouth, not only the TMJ but also the surrounding muscles and the central nervous system are required to participate. During the consultation and treatment of temporomandibular joint disorders, it was found that in addition to displacement of the joint disc that can cause mouth opening pain, bone tumors, muscle spasm, peripheral neuritis (trigeminal nerve, linguopharyngeal nerve), etc. can cause the symptom. The patient was a male with pain in the left preauricular region for 10 days. MR showed irreducible disc displacement of the left temporomandibular joint disc and bilateral condylar bone changes. The first diagnosis was “temporomandibular joint disorder”, and after 1 week of physiotherapy with manipulation and acupuncture treatment, the symptoms were not significantly relieved, so neuropathy was considered and later diagnosed as “linguopharyngeal neuritis”. Therefore, the painful opening of the mouth is closely related to TMJ, but at the same time, we need to exclude other diseases that may cause such symptoms, make the correct diagnosis, choose the appropriate treatment plan, so that the pain is away from you and me as soon as possible.