The pain on the left side of the jaw may be caused by trauma, or by diseases such as temporomandibular joint disorder syndrome, lymphadenitis, or other diseases such as cervical spondylosis. 1. Trauma: If the patient’s jaw has suffered an impact, it can cause the patient to experience pain on the left side of the jaw. 2. Temporomandibular joint disorder syndrome: the cause of temporomandibular joint disorder syndrome is not yet clear, and it is considered to be caused by a variety of factors such as trauma inside and outside the joints, depression, anxiety and so on. The main symptoms of temporomandibular joint disorder syndrome are limited jaw movement, pain in opening and closing the mouth, teeth grinding, etc. Difficulty in opening the mouth and pain in the temporomandibular joint area also occur. 3. Lymphadenitis: Lymphadenitis is mainly caused by bacterial and other pathogen infections, and patients will have swollen and painful lymph nodes. If the patient has inflammation of the lymph nodes in the neck, it will cause the patient to have pain on the left side of the jaw. 4. Other: cervical spondylosis, stem syndrome and other diseases can also cause patients to have pain in the left side of the jaw. There are many reasons for patients to have pain on the left side of the jaw, they should seek medical treatment in time and follow the doctor’s instructions.