By far the most common condition is TMJ pain dysfunction syndrome (TMJPDS)/facial arthromyalgia (3% to 5% of the population will seek treatment).
The TMJ is a synovial joint in which the mandibular condyle articulates with the base of the skull at the glenoid fossa and articular eminence. Interposed between the two is the articular disc or meniscus, the function of which is to contribute to the smooth action of the joint. The disc is also believed to be involved in many of the disorders commonly seen. The disc is divided into three zones – a thick posterior band, a thin intermediate zone and a slightly thicker but narrow anterior band.