temporomandibular joint dysfunction temporomandibular joint dysfunction temporomandibular joint dysfunction (tmd, tmjd) is an umbrella term covering pain and dysfunction of the muscles of mastication (the muscles that move the jaw) and the temporomandibular joints (the joints which connect the mandible to the skull). the most important feature is pain, followed by restricted mandibular movement, and noises from the temporomandibular joints (tmj) during jaw movement. although tmd is not life-threatening, it can be detrimental to quality of life; this is because the symptoms can become chronic and difficult to manage. this article is about the syndrome with joint pain. for the range of diseases affecting the joint, see temporomandibular joint pathology. temporomandibular joint dysfunctionother namestemporomandibular joint dysfunction syndrome, temporomandibular disorder, otherstemporomandibular jointspecialtyoral and maxillofacial surgery, oral medicine in this article, the term temporomandibular disorder is taken to mean any disorder that affects the temporomandibular joint, and temporomandibular joint dysfunction (here also abbreviated to tmd) is taken to mean symptomatic (e.g. pain, limitation of movement, clicking) dysfunction of the temporomandibular joint. however, there is no single, globally accepted term or definition concerning this topic. 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. however, these factors are poorly understood, and there is disagreement as to their relative importance. there are many treatments available, although there is a general lack of evidence for any treatment in tmd, and no widely accepted treatment protocol. common treatments include provision of occlusal splints, psychosocial interventions like cognitive behavioral therapy, physical therapy, and pain medication or others. most sources agree that no irreversible treatment should be carried out for tmd. about 20% to 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 after dental pain (i.e. toothache). classification classification: muscular: hyperactivity, spasm, and trismus inflammation (myositis) trauma myofascial pain and fibromyalgia atrophy or hypertrophy arthrogenic: disc displacement (internal derangement) hypomobility of the disc (adhesions or scars) dislocation and subluxation arthritis infections metabolic disease (gout, chondrocalcinosis) capsulitis, synovitis ankylosis (fibrous or bony) fracture absent, large, or small condyloid process neoplasia tmd is considered by some to be one of the 4 major symptom complexes in chronic orofacial pain, along with burning mouth syndrome, atypical facial pain and atypical odontalgia. tmd has been considered as a type of musculoskeletal, neuromuscular, or rheumatological disorder. it has also been called a functional pain syndrome, and a psychogenic disorder. others consider tmd a "central sensitivity syndrome", in reference to evidence that tmd might be caused by a centrally mediated sensitivity to pain. it is hypothesized that there is a great deal of similarity between tmd and other pain syndromes like fibromyalgia, irritable bowel syndrome, interstitial cystitis, headache, chronic lower back pain and chronic neck pain. these disorders have also been theorized to be caused by centrally mediated sensitivity to pain, and furthermore they often occur together. definitions and terminology frequently, tmd has been treated as a single syndrome, but the prevailing modern view is that tmd is a cluster of related disorders with many common features. indeed, some have suggested that, in the future, the term tmd may be discarded as the different causes are fully identified and separated into different conditions. sometimes, "temporomandibular joint dysfunction" is described as the most common form of temporomandibular disorder, whereas many other sources use the term temporomandibular disorder synonymously, or instead of the term temporomandibular joint dysfunction. in turn, the term temporomandibular disorder is defined as "musculoskeletal disorders affecting the temporomandibular joints and their associated musculature. it is a collective term which represents a diverse group of pathologies involving the temporomandibular joint, the muscles of mastication, or both". another definition of temporomandibular disorders is "a group of conditions with similar signs and symptoms that affect the temporomandibular joints, the muscles of mastication, or both." temporomandibular disorder is a term that creates confusion since it refers to a group of similarly symptomatic conditions, whilst many sources use the term temporomandibular disorders as a vague description, rather than a specific syndrome, and refer to any condition which may affect the temporomandibular joints (see table). the temporomandibular joint is susceptible to a huge range of diseases, some rarer than others, and there is no implication that all of these will cause any symptoms or limitation in function at all. the preferred terms in medical publications is to an extent influenced by geographic location. for example, in the united kingdom, the term pain dysfunction syndrome is in common use. in the united states, the term temporomandibular disorder is generally favored. the american academy of orofacial pain uses temporomandibular disorder, whilst the national institute of dental and craniofacial research uses temporomandibular joint disorder. a more complete list of synonyms for this topic is extensive, with some being more commonly used than others. in addition to those already mentioned, examples include temporomandibular joint pain dysfunction syndrome, temporomandibular pain dysfunction syndrome, temporomandibular joint syndrome, temporomandibular dysfunction syndrome, temporomandibular dysfunction, temporomandibular disorder, temporomandibular syndrome, facial arthromyalgia, myofacial pain dysfunction syndrome, craniomandibular dysfunction (cmd), myofacial pain dysfunction, masticatory myalgia, mandibular dysfunction, and costen's syndrome. the lack of standardization in terms is not restricted to medical papers. notable internationally recognized sources vary in both their preferred term, and their offered definition. for example: "temporomandibular pain and dysfunction syndrome – aching in the muscles of mastication, sometimes with an occasional brief severe pain on chewing, often associated with restricted jaw movement and clicking or popping sounds." (classification of chronic pain, international association for the study of pain). "headache or facial pain attributed to temporomandibular joint disorder." (international classification of headache disorders 2nd edition (ichd-2), international headache society). "temporomandibular joint-pain-dysfunction syndrome" listed in turn under "temporomandibular joint disorders" (international classification of diseases 10th revision, world health organization). by cause and symptoms it has been suggested that tmd may develop following physical trauma, particularly whiplash injury, although the evidence for this is not conclusive. this type of tmd is sometimes termed "posttraumatic tmd" (ptmd) to distinguish it from tmd of unknown cause, sometimes termed "idiopathic tmd" (itmd). sometimes muscle-related (myogenous) tmd (also termed myogenous tmd, or tmd secondary to myofascial pain and dysfunction) is distinguished from joint-related tmd (also termed arthogenous tmd, or tmd secondary to true articular disease), based upon whether the muscles of mastication or the tmjs themselves are predominantly involved. this classification, which effectively divides tmd into 2 syndromes, is followed by the american academy of orofacial pain. however, since most people with tmd could be placed into both of these groups, which makes a single diagnosis difficult when this classification is used. the research diagnostic criteria (rdc/tmd) allows for multiple diagnoses in an attempt to overcome the problems with other classifications. rdc/tmd considers temporomandibular disorders in 2 axes; axis i is the physical aspects, and axis ii involves assessment of psychological status, mandibular function and tmd-related psychosocial disability. axis i is further divided into 3 general groups. group i are muscle disorders, group ii are disc displacements and group iii are joint disorders, although it is common for people with tmd to fit into more than one of these groups. by duration sometimes distinction is made between acute tmd, where symptoms last for less than 3 months, and chronic tmd, where symptoms last for more than 3 months. not much is known about acute tmd since these individuals do not typically attend in secondary care (hospital). signs and symptoms signs and symptoms of temporomandibular joint disorder vary in their presentation. the symptoms will usually involve more than one of the various components of the masticatory system, muscles, nerves, tendons, ligaments, bones, connective tissue, or the teeth. the three classically described, cardinal signs and symptoms of tmd are: pain and tenderness on palpation in the muscles of mastication, or of the joint itself (preauricular pain – pain felt just in front of the ear). pain is the defining feature of tmd and is usually aggravated by manipulation or function, such as when chewing, clenching, or yawning, and is often worse upon waking. the character of the pain is usually dull or aching, poorly localized, and intermittent, although it can sometimes be constant. the pain is more usually unilateral (located on one side) rather than bilateral. it is rarely severe. limited range of mandibular movement, which may cause difficulty eating or even talking. there may be locking of the jaw, or stiffness in the jaw muscles and the joints, especially present upon waking. there may also be incoordination, asymmetry or deviation of mandibular movement. noises from the joint during mandibular movement, which may be intermittent. joint noises may be described as clicking, popping, or crepitus (grating). tmj dysfunction is commonly associated with symptoms affecting cervical spine dysfunction and altered head and cervical spine posture. other signs and symptoms have also been described, although these are less common and less significant than the cardinal signs and symptoms listed above. examples include: headache (possibly), e.g. pain in the occipital region (the back of the head), or the forehead; or other types of facial pain including migraine, tension headache, or myofascial pain. pain elsewhere, such as the teeth or neck. diminished auditory acuity (hearing loss). tinnitus (occasionally). dizziness. sensation of malocclusion (feeling that the teeth do not meet together properly). causes tmd is a symptom complex (i.e. a group of symptoms occurring together and characterizing a particular disease), which is thought to be caused by multiple, poorly understood factors, but the exact etiology is unknown. there are factors which appear to predispose to tmd (genetic, hormonal, anatomical), factors which may precipitate it (trauma, occlusal changes, parafunction), and also factors which may prolong it (stress and again parafunction). overall, two hypotheses have dominated research into the causes of tmd, namely a psychosocial model and a theory of occlusal dysharmony. interest in occlusal factors as a causative factor in tmd was especially widespread in the past, and the theory has since fallen out of favor and become controversial due to lack of evidence. disc displacement in people with tmd, it has been shown that the lower head of lateral pterygoid contracts during mouth closing (when it should relax), and is often tender to palpation. to theorize upon this observation, some have suggested that due to a tear in the back of the joint capsule, the articular disc may be displaced forwards (anterior disc displacement), stopping the upper head of lateral pterygoid from acting to stabilize the disc as it would do normally. as a biologic compensatory mechanism, the lower head tries to fill this role, hence the abnormal muscle activity during mouth closure. there is some evidence that anterior disc displacement is present in a proportion of tmd cases. anterior disc displacement with reduction refers to abnormal forward movement of the disc during opening which reduces upon closing. anterior disc displacement without reduction refers to an abnormal forward, bunched-up position of the articular disc which does not reduce. in this latter scenario, the disc is not intermediary between the condyle and the articular fossa as it should be, and hence the articular surfaces of the bones themselves are exposed to a greater degree of wear (which may predispose to osteoarthritis in later life). degenerative joint disease the general term "degenerative joint disease" refers to arthritis (both osteoarthritis and rheumatoid arthritis) and arthrosis. the term arthrosis may cause confusion since in the specialized tmd literature it means something slightly different from in the wider medical literature. in medicine generally, arthrosis can be a nonspecific term for a joint, any disease of a joint (or specifically degenerative joint disease), and is also used as a synonym for osteoarthritis. in the specialized literature that has evolved around tmd research, arthrosis is differentiated from arthritis by the presence of low and no inflammation respectively. both are however equally degenerative. the tmjs are sometimes described as one of the most used joints in the body. over time, either with normal use or with parafunctional use of the joint, wear and degeneration can occur, termed osteoarthritis. rheumatoid arthritis, an autoimmune joint disease, can also affect the tmjs. degenerative joint diseases may lead to defects in the shape