Temporomandibular joint dysfunction (sometimes abbreviated to TMD or TMJD and also termed temporomandibular joint dysfunction syndrome, temporomandibular disorder or many other names), is an umbrella term covering pain and dysfunction of the muscles of mastication. In layman’s terms that means when the muscles that move the jaw and the joints which connect the jaw to the skull. The most important feature of TMD is pain, followed by restricted jaw movement, and noises from the joints (TMJ) during jaw movement. Although TMD is not life-threatening, it can be detrimental to quality of life because the symptoms can become chronic and difficult to manage. TMD is thought to be very common. About 20-30% of the adult population are affected to some degree. Usually people affected by TMD are between 20 and 40 years of age, and it is more common in females than males. TMD is the second most frequent cause of orofacial pain (dental pain is the first cause, for example a toothache).
TMD is a symptom complex rather than a single condition, and it is thought to be caused by multiple factors.