A balance exists between how the teeth fit together, how the joints work, and the muscle function that move the jaws. When this balance is disrupted something has to give. The joints may become dislocated (click / pop), the teeth may wear down or lose bone support, or the muscles may become sore (headaches / neck aches).
It is possible to open your mouth by just moving your head. The pictures show the lady with her lower jaw in her hand and her elbow on the table. She opens by moving her head up and down. The short muscles in the back of the neck don’t take long to complain (neck ache).
The back wall of the jaw joint is the front wall of the ear canal. Arteries, veins, and nerves and a ligament connect between the jaw and the ear. There is a structural, functional and postural connection between the jaw and the ear, which can lead to pain. The picture below of a dislocated jaw shows the ball of the joint sitting on the arteries, veins and nerves.