TMJ disorder is increasingly defined as a condition that can affect more than one local area of the body. If you have some signs of TMJ disorder, such as jaw grinding, trouble opening your mouth, jaw lock, headache, ear pain, or jaw tenderness, and you might also have an arm, shoulder, and back pain, they could all be related. Everything in your body is linked, and when something is out of balance, it can affect other parts of the body.