surface and the infratemporal crest of the greater wing of the sphenoid bone. 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. the 2 parts of lateral pterygoid have different actions. the lower head contracts during mouth opening, and the upper head contracts during mouth closing. the function of the lower head is to steady the articular disc as it moves back with the condyle into the articular fossa. it is relaxed during mouth closure. 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. 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. 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. crepitus often indicates arthritic changes in the joint, and may occur at any time during mandibular movement, especially lateral movements. perforation of the disc may also cause crepitus. due to the proximity of the tmj to the 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. 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. limitation of mandibular movement the jaw deviates to the affected side during opening, and restricted mouth opening usually signifies that both tmjs are involved, but severe trismus rarely occurs. if the greatest reduction in movement occurs upon waking then this may indicate that there is concomitant sleep bruxism. in other cases the limitation in movement gets worse throughout the day. the jaw may lock entirely. 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. the muscles become weak, and fibrosis may occur. all these factors may lead to a further limitation of jaw movement and increase in pain. 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. 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. due to the proximity of the ear to the temporomandibular joint, tmj pain can often be confused with ear pain. the pain may be referred in around half of all patients and experienced as otalgia (earache). conversely, tmd is an important possible cause of secondary otalgia. treatment of tmd may then significantly reduce symptoms of otalgia and tinnitus, as well as atypical facial pain. 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. diagnosis rdc/tmd criteria, axis i diagnoses. group i: muscle disorders ia. myofascial pain: report of pain or ache in the jaw, temples, face, preauricular area, or inside the ear at rest or during function; pain reported by the subject in response to palpation of 3 of the following muscle sites (right side and left side count as a separate sites for each muscle): posterior temporalis, middle temporalis, anterior temporalis, origin of masseter, insertion of masseter, posterior mandibular region, submandibular region, lateral pterygoid area, and tendon of the temporalis; at least one of the painful sites must be on the same side as the complaint of pain. ib. myofascial pain with limited opening: myofascial pain as defined in ia; pain-free unassisted mandibular opening 40 mm; maximum assisted opening (passive stretch) 5 mm greater than pain-free unassisted opening. group ii: disc displacements iia. disc displacement with reduction: reciprocal clicking in tmj (click on both vertical opening and closing that occurs at point 5 mm greater interincisal distance on opening than closing and is eliminated on protrusive opening), reproducible on 2 out of 3 consecutive trials; or clicking in tmj on both vertical range of motion (either opening or closing), reproducible on 2 out of 3 consecutive trials, and click during lateral excursion or protrusion, reproducible on 2 out of 3 consecutive trials. iib. disc displacement without reduction with limited opening: history of significant limitation in opening; maximum unassisted opening 35 mm; passive stretch increases opening by 4 mm over maximum unassisted opening; contralateral excursion 7 mm or uncorrected deviation to ipsilateral side on opening; absence of joint sound or presence of joint sounds not meeting criteria for disc displacement with reduction. iic. disc displacement without reduction, without limited opening: history of significant limitation of mandibular opening; maximum unassisted opening 35 mm; passive stretch increases opening by 5 mm over maximum unassisted opening; contralateral excursion 7 mm; presence of joint sounds not meeting criteria for disc displacement with reduction; in those studies allowing images, imaging conducted by either arthrography or magnetic resonance reveals disc displacement without reduction. group iii: arthralgia, osteoarthritis, osteoarthrosis iiia. arthralgia: pain in one or both joint sites (lateral pole or posterior attachment) during palpation; one or more of the following self-reports of pain: pain in the region of the joint, pain in the joint during maximum unassisted opening, pain in the joint during assisted opening, and pain in the joint during lateral excursion; for a diagnoses of simple arthralgia, coarse crepitus must be absent. iiib. osteoarthritis of the tmj: arthralgia as defined in iiia; either coarse crepitus in the joint or radiologic signs of arthrosis. iiic. osteoarthrosis of the tmj: absence of all signs of arthralgia; either coarse crepitus in the joint or radiologic signs of arthrosis modern digitalised panoramic x-ray devices are capable to take tmj images, which provides information about articular fossa and condyle. pain is the most common reason for people with tmd to seek medical advice. joint noises may require auscultation with a stethoscope to detect. clicks of the joint may also be palpated, over the joint itself in the preauricular region, or via a finger inserted in the external acoustic meatus, which lies directly behind the tmj. the differential diagnosis is with degenerative joint disease (e.g. osteoarthritis), rheumatoid arthritis, temporal arteritis, otitis media, parotitis, mandibular osteomyelitis, eagle syndrome, trigeminal neuralgia, oromandibular dystonia, deafferentation pains, and psychogenic pain. diagnostic criteria various diagnostic systems have been described. some consider the research diagnostic criteria method the gold standard. 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. this method involves 2 diagnostic axes, namely axis i, the physical diagnosis, and axis ii, the psychologic diagnosis. axis i contains 3 different groups which can occur in combinations of 2 or all 3 groups, (see table). mcneill 1997 described tmd diagnostic criteria as follows: pain in muscles of mastication, the tmj, or the periauricular area (around the ear), which is usually made worse by manipulation or function. asymmetric mandibular movement with or without clicking. limitation of mandibular movements. pain present for a minimum of 3 months. the international headache society's diagnostic criteria for "headache or facial pain attributed to temporomandibular joint disorder" is similar to the above: a. recurrent pain in one or more regions of the head or face fulfilling criteria c and d b. x-ray, mri or bone scintigraphy demonstrate tmj disorder c. evidence that pain can be attributed to the tmj disorder, based on at least one of the following: pain is precipitated by jaw movements or chewing of hard or tough food reduced range of or irregular jaw opening noise from one or both tmjs during jaw movements tenderness of the joint capsule(s) of one or both tmjs d. headache resolves within 3 months, and does not recur, after successful treatment of the tmj disorder medical imaging the advantages brought about by diagnostic imaging mainly lie within diagnosing tmd of articular origin. additional benefits of imaging the tmj are as follows: assess the integrity of anatomical structures in suspicion of disorders staging the extent of any pathology monitoring and staging the progress of disease determining the effects of treatment when clinical examination alone is unable to bring sufficient detail to ascertain the state of the tmj, imaging methods can act as an adjuvant to clinical examination in the diagnosis of tmd. plain radiography this method of imaging allows the visualisation of the joint's mineralised areas, therefore excluding the cartilage and soft tissues. a disadvantage of plain radiography is that images are prone to superimposition from surrounding anatomical structures, thereby complicating radiographic interpretation. it was concluded that there is no evidence to support the use of plain radiography in the diagnosis of joint erosions and osteophytes. it is reasonable to conclude that plain film can only be used to diagnose extensive lesions. panoramic tomography the distortion brought about by panoramic imaging decreases its overall reliability. data concluded from a systematic review showed that only extensive erosions and large osteophytes can be detected by panoramic imaging. computerised tomography (ct) studies have shown that tomography of the tmj provided supplementary information that supersedes what is obtainable from clinical examination alone. however, the issues lies in the fact that it is impossible to determine whether certain patient groups would benefit more or less from a radiographic examination. 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. the introduction of cone beam computed tomography (cbct) imaging allowed a lower radiation dose to patients, in comparison to conventional ct. hintze et al. compared cbct and ct techniques and their ability to detect morphological tmj changes. no significant difference was concluded in terms of their diagnostic accuracy. magnetic resonance imaging (mri) mri is the optimal choice for the imaging of soft tissues surrounding the tmj. it allows three-dimensional evaluation of the axial, coronal and sagittal plane. it is the gold standard method for assessing disc position and is sensitive for intra-articular degenerative alterations. 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. it is also useful for assessing the integrity of neural tissues, which may produce orofacial pain when compressed. mri provides evaluation of pathology such as necrosis and oedema all without any exposure to ionizing radiation. however, there is a high cost associated with this method of imaging, due to the need for sophisticated facilities. 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. ultrasound where internal tmj disorders are concerned, ultrasound (us) imaging can be a useful alternative in assessing the position of the disc while having