When you have pain in the facial area its usually a warning sign, as with any pain, that the jaw joint is in dysfunction. TMJ is a musculoskeletal condition that is often caused by clenching of the teeth. This causes the chewing muscles to tighten and clamp down on the jaw inhibiting full range of motion and causing pain. Since the chewing muscle shares functions with the neck, its dysfunction is the cause of headaches and neck pain.