The joint is a hinge that connects your jaw to the temporal bones of your skull, which are in front of each ear. It lets you move your jaw up and down and side to side, so you can chew, talk and yawn. The causes of TMD are from injuries directly to the jaw, joint, or the muscles of your head and neck, like from a heavy blow or whiplash. Things like grinding and clenching your teeth can also place pressure. Arthritis or stress can be other causes.