Pain at the ear joint when opening the mouth can be caused by temporomandibular joint disorder syndrome, facial soft tissue injury, ligament laxity around temporomandibular joint and other factors. 1. Temporomandibular joint disorder syndrome: injury or pain around the temporomandibular joint can lead to dysfunction of the masticatory muscles, which is common in people who are used to unilateral mastication, and ear pain can occur when opening the mouth. 2. Facial soft tissue injury: after local trauma to facial muscles and chewing muscles, swelling, ecchymosis, restricted movement and other symptoms may occur, which may lead to the involvement of the injured place when opening the mouth, and then ear pain may occur when opening the mouth. 3. Laxity of ligaments around the temporomandibular joint: when the ligaments around the temporomandibular joint and other tissues become lax, it can lead to the manifestation of dislocation of the mandibular joint, which can aggravate the discomfort symptoms when opening the mouth, and the pain in the ear and other parts of the body can appear. If you have pain in the ear joint when opening your mouth, you should consult a doctor in time and take appropriate treatment under the guidance of a specialist.