Editing Temporomandibular joint dysfunction (section)

===Mechanisms of symptoms===

====Joint noises====
Noises from the TMJs are a symptom of dysfunction of these joints. The sounds commonly produced by TMD are usually described as a "click" or a "pop" when a single sound is heard and as "crepitation" or "crepitus" when there are multiple, grating, rough sounds. Most joint sounds are due to internal derangement of the joint, which is instability or abnormal position of the articular disc.<ref name="Odell 2010">{{cite book|veditors=Odell EW|title=Clinical problem solving in dentistry|url=https://archive.org/details/clinicalproblems00odel|url-access=limited|year=2010|publisher=Churchill Livingstone |location=Edinburgh|isbn=9780443067846|pages=[https://archive.org/details/clinicalproblems00odel/page/n47 37]–41|edition=3rd}}</ref> Clicking often accompanies either jaw opening or closing, and usually occurs towards the end of the movement. The noise indicates that the articular disc has suddenly moved to and from a temporarily displaced position (disk displacement with reduction) to allow completion of a phase of movement of the mandible.<ref name="Scully 2008" /><ref name="Glick 2003" /> If the disc displaces and does not reduce (move back into position) this may be associated with locking. Clicking alone is not diagnostic of TMD since it is present in high proportion of the general population, mostly in people who have no pain.<ref name="Scully 2008" /> Crepitus often indicates arthritic changes in the joint, and may occur at any time during mandibular movement, especially lateral movements.<ref name="Scully 2008" /> Perforation of the disc may also cause crepitus.<ref name="Kerawala 2010" /> Due to the proximity of the TMJ to the [[external auditory meatus|ear canal]], joint noises are perceived to be much louder to the individual than to others. Often people with TMD are surprised that what sounds to them like very loud noises cannot be heard at all by others next to them. However, it is occasionally possible for loud joint noises to be easily heard by others in some cases and this can be a source of embarrassment e.g. when eating in company.

====Pain====
Pain symptoms in TMD can be thought of as originating from the joint (arthralgia), or from the muscles (myofascial), or both. There is a poor correlation between TMD pain severity and evidence of tissue pathology.<ref name="Cairns 2010" />

Generally, degenerative joint changes are associated with greater pain.

=====Myofascial Pain=====
Pain originating from the muscles of mastication as a result of abnormal muscular function or hyperactivity. The muscular pain is frequently, but not always, associated with daytime clenching or nocturnal bruxism.<ref>Contemporary Oral and Maxillofacial Surgery fifth edition; Hupp, ellis, and tucker. 2008</ref>

====Limitation of mandibular movement====
The jaw deviates to the affected side during opening,<ref name="Classification of Chronic Pain" /> and restricted mouth opening usually signifies that both TMJs are involved, but severe [[trismus]] rarely occurs.<!-- <ref name="Scully 2008" /> --> If the greatest reduction in movement occurs upon waking then this may indicate that there is concomitant sleep bruxism.<!-- <ref name="Scully 2008" /> --> In other cases the limitation in movement gets worse throughout the day.<ref name="Scully 2008" />

The jaw may lock entirely.<ref name="Scully 2008" />

Limitation of mandibular movement itself may lead to further problems involving the TMJs and the muscles of mastication. Changes in the synovial membrane may lead to a reduction in lubrication of the joint and contribute to degenerative joint changes.<ref name="Hupp 2008" /> The muscles become weak, and [[fibrosis]] may occur. All these factors may lead to a further limitation of jaw movement and increase in pain.<ref name="Hupp 2008" />

Degenerative joint disease, such as osteoarthritis or organic degeneration of the articular surfaces, recurrent fibrous or bony ankylosis, developmental abnormality, or pathologic lesions within the TMJ. [[Myofascial pain syndrome]].{{medical citation needed|date=May 2013}}

=====Referred TMD pain=====
Sometimes TMD pain can radiate or be referred from its cause (i.e. the TMJ or the muscles of mastication) and be felt as headaches, earache or toothache.<ref name="Neville 2001" />

Due to the proximity of the ear to the temporomandibular joint, TMJ pain can often be confused with ear pain.<ref name="Okeson 2003" /> The pain may be [[referred pain|referred]] in around half of all patients and experienced as [[otalgia]] (earache).<ref name="pmid15800464">{{cite journal | vauthors = Ramírez LM, Sandoval GP, Ballesteros LE | title = Temporomandibular disorders: referred cranio-cervico-facial clinic | journal = Medicina Oral, Patologia Oral y Cirugia Bucal | volume = 10 | issue = Suppl 1 | pages = E18-26 | date = April 2005 | pmid = 15800464 | url = http://www.medicinaoral.com/medoralfree01/v10Suppl1i/medoralv10suppl1ip18.pdf }}</ref> Conversely, TMD is an important possible cause of [[Otalgia#Secondary otalgia|secondary otalgia]]. Treatment of TMD may then significantly reduce symptoms of otalgia and [[tinnitus]], as well as [[atypical facial pain]].<ref name="pmid16113700">{{cite journal | vauthors = Quail G | title = Atypical facial pain--a diagnostic challenge | journal = Australian Family Physician | volume = 34 | issue = 8 | pages = 641–5 | date = August 2005 | pmid = 16113700 | url = http://www.racgp.org.au/afp/downloads/pdf/august2005/August_theme_quail2.pdf | access-date = 23 July 2006 | archive-date = 16 November 2006 | archive-url = https://web.archive.org/web/20061116040924/http://www.racgp.org.au/afp/downloads/pdf/august2005/August_theme_quail2.pdf | url-status = dead }}</ref> Despite some of these findings, some researchers question whether TMJD therapy can reduce symptoms in the ear, and there is currently an ongoing debate to settle the controversy.<ref name="Okeson 2003" />