TMDs have a range of causes and often co-occur with a number of overlapping medical conditions, including headaches, fibromyalgia, back pain, and irritable bowel.

[6] Emotional stress (anxiety, depression, anger) may increase pain by causing autonomic, visceral and skeletal activity and by reduced inhibition via the descending pathways of the limbic system.

[27][30] In the 6 months before the onset, 50–70% of people with TMD report experiencing stressful life events (e.g. involving work, money, health or relationship loss).

[35] Other parafunctional habits such as pen chewing, lip and cheek biting (which may manifest as morsicatio buccarum or linea alba), are also suggested to contribute to the development of TMD.

This may occur during dental treatment, with oral intubation whilst under a general anesthetic, during singing or wind instrument practice (really these can be thought of as parafunctional activities).

[27] Damage may be incurred during violent yawning, laughing, road traffic accidents, sports injuries, interpersonal violence, or during dental treatment,[25] (such as tooth extraction).

[27] It has been proposed that a link exists between whiplash injuries (sudden neck hyper-extension usually occurring in road traffic accidents), and the development of TMD.

This has been postulated to be explained by variations of the gene which codes for the enzyme catechol-O-methyl transferase (COMT) which may produce 3 different phenotypes with regards pain sensitivity.

Estrogen may play a role in modulating joint inflammation, nociceptive neurons in the trigeminal nerve, muscle reflexes to pain and μ-opioid receptors.

[17] A possible link between many of these chronic pain conditions has been hypothesized to be due to shared pathophysiological mechanisms, and they have been collectively termed "central sensitivity syndromes",[17] although other apparent associations cannot be explained in this manner.

The upper head also inserts at the fovea, but a part may be attached directly to the joint capsule and to the anterior and medial borders of the articular disc.

[49] 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.

[medical citation needed] 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.

The differential diagnosis is with degenerative joint disease (e.g. osteoarthritis), rheumatoid arthritis, temporal arteritis, otitis media, parotitis, mandibular osteomyelitis, Eagle syndrome, trigeminal neuralgia,[medical citation needed] oromandibular dystonia,[medical citation needed] deafferentation pains, and psychogenic pain.

[19] Abbreviated to "RDC/TMD", this was first introduced in 1992 by Dworkin and LeResche in an attempt to classify temporomandibular disorders by etiology and apply universal standards for research into TMD.

[57] The main indications of CT and CBCT examinations are to assess the bony components of the TMJ, specifically the location and extent of any abnormalities present.

[62] Indications for MRI are pre-auricular pain, detection of joint clicking and crepitus, frequent incidents of subluxation and jaw dislocation, limited mouth opening with terminal stiffness, suspicion of neoplastic growth, and osteoarthritic symptoms.

[58] Caution should be taken in patient selection, as MRI is contraindicated in those with claustrophobic tendencies, pacemakers and metallic heart valves, ferromagnetic foreign bodies and pregnant women.

[64] Where internal TMJ disorders are concerned, ultrasound (US) imaging can be a useful alternative in assessing the position of the disc[65][66] While having significant diagnostic sensitivity, US has inadequate specificity when identifying osteoarthrosis.

[64][66] in addition to being less costly,[59] US provides a quick and comfortable real-time imaging without exposing the individual to ionizing radiation[65][66][67] US is commonly assessed in the differential diagnosis of alterations of glandular and neighbouring structures, such as the TMJ and the masseter muscle.

[68] TMD can be difficult to manage, and since the disorder transcends the boundaries between several health-care disciplines – in particular, dentistry and neurology, the treatment may often involve multiple approaches and be multidisciplinary.

[18] It is more complicated to construct than other types of splint since a face bow record is required and significantly more skill on the part of the dental technician.

Examples of partial coverage splints include the NTI-TSS ("nociceptive trigeminal inhibitor tension suppression system"), which covers the upper front teeth only.

A baseline record of the distance at the start of physical therapy (e.g. the number of fingers that can be placed vertically between the upper and lower incisors), can chart any improvement over time.

[81] This is the adjustment or reorganizing of the existing occlusion, carried out in the belief that this will redistribute forces evenly across the dental arches or achieve a more favorable position of the condyles in the fossae, which is purported to lessen tooth wear, bruxism and TMD, but this is controversial.

"[16] A common scenario where a newly placed dental restoration (e.g. a crown or a filling) is incorrectly contoured, and creates a premature contact in the bite.

Examples of surgical procedures that are used in TMD, some more commonly than others, include arthrocentesis,[75] arthroscopy, meniscectomy, disc repositioning, condylotomy or joint replacement.

[90] It has been suggested that TMD does not cause permanent damage and does not progress to arthritis in later life,[25]: 174–175  however, degenerative disorders of the TMJ such as osteoarthritis are included within the spectrum of TMDs in some classifications.

[91][92] Costen was an otolaryngologist,[93] and although he was not the first physician to describe TMD, he wrote extensively on the topic, starting in 1934, and was the first to approach the disorder in an integrated and systematic way.

[94] Costen hypothesized that malocclusion caused TMD, and placed emphasis on ear symptoms, such as tinnitus, otalgia, impaired hearing, and even dizziness.