The term TMJ is shorthand for temporomandibular joint and refers to the joint between the condyle of your mandible (lower jaw) and the glenoid fossa (skull base). The joints are unique in that they both function together at the same time to open or close your mouth.
TMJs are ginglymoarthroidal joints as they hinge open (the initial bit of opening) and then slide forwards (allowing you to open fully). In between the two surfaces of the joint is an articular meniscus or disc made out of cartilage. Problems you may have with TMJ are: associated with muscles around the TMJ, often as a result of habitual clenching and/or grinding, sometimes termed myofascial pain; problems with the joint itself as a result of internal joint derangement, in which the movements are not as smooth as they should be on opening and/or closing; problems with the joint due to degenerative diseases such as arthritis; pyschosocial problems due to stress and/or anxiety, sometimes termed “functional overlay”. Symptoms of TMD vary from person to person (and depend upon the causative pathologies), but common ones include: pain, limitation of mouth opening (trismus), jaw locking, crunching, grinding and/or clicking noises and associated headache.
As TMD (temporomandibular disorder) is multifactorial in terms of the underlying causes, treatment is similarly often multimodal and may be done in a stepwise fashion according to response. Common treatments include: TMJ physiotherapy and exercises, medication, stress relief, occlusal appliances (splints), TMJ arthroscopy, open TMJ surgery (TMJ arthroplasty), total prosthetic (alloplastic) TMJ replacement.