TMD is a complex issues. Just to be brief, TMD can be caused by degeneration in the joint, subluxation (lock jaw), pain. Signs include wear facets, palpable muscles of mastication, headaches and poor posture (head toward). Clenching, bruxism, trauma, arthritis in the jaw can lead to TMD. CBCT (cone beam), possibly MRI can be used to confirm diagnosis. Initial treatment should be a nightguard with palliative remedies ( warm compress, massage and inti-inflammatory meds) before a more invasive surgery. Hope this helps.