TMJ Examination
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Direct answer
Palpate, listen, measure and load — a complete TMJ screen takes under two minutes. Palpate the lateral pole (finger just anterior to the tragus) and the posterior pole (little finger in the external meatus) during opening and closing; palpate the muscles of mastication; listen with a stethoscope for clicks (disc displacement with reduction) or crepitus (degenerative change); and measure mandibular movements — normal interincisal opening 35–55 mm, lateral excursion 8–12 mm, protrusion about 6–10 mm — recording any deviation or deflection of the midline. One exam fact earns marks by itself: the lateral pterygoid cannot be reliably palpated clinically.
What you must remember
- Lateral pole: palpate with the index finger placed just anterior to the tragus while the patient opens and closes; posterior pole: little finger in the ear canal pressing forwards.
- Muscles to palpate: masseter (zygomatic arch and angle), temporalis (temporal fossae and anterior border intraorally at the coronoid), medial pterygoid (inner aspect of the angle, bimanually) — lateral pterygoid is not directly palpable.
- Normal values: maximum interincisal opening 35–55 mm (less than about 30 mm suggests restriction), lateral excursions 8–12 mm each side, protrusion 6–10 mm.
- Deviation means the midline shifts but returns to centre at maximum opening; deflection means it stays off-centre at maximum opening (typical of disc displacement without reduction or ankylosis on the restricted side).
- Clicks: a reciprocal click (on opening and again near closure) with near-normal opening indicates disc displacement with reduction; crepitus — grating, crunching — indicates degenerative joint disease with disc perforation or surface wear.
- Screen the cranial nerve contribution: jaw-opening reflex symmetry, facial nerve, and note facial asymmetry at rest and on function.
- Always examine the muscles as carefully as the joints — myofascial pain is the commonest temporomandibular disorder, with localised tender bands and referred pain patterns.
- Imaging is matched to the question: OPG for survey, specific TMJ views for gross bony change, CBCT for cortical detail, MRI for the disc.
A typical exam case
A 28-year-old woman reports two years of clicking on the right jaw with morning stiffness; for the past week the click has disappeared and opening feels "stuck". Inspection shows no asymmetry, but the mandible deflects to the right at maximum opening. Measurement: interincisal opening 29 mm, right lateral excursion full but left excursion reduced.
Now interpret. The history describes years of disc displacement with reduction — a reciprocal click — followed by an episode where the click vanished and opening dropped: the classic progression to disc displacement without reduction, the stuck disc blocking translation on the right. The signs confirm it: deflection towards the affected side at maximum opening and restricted contralateral excursion, because translation of the right condyle is what drives left excursion. Palpation adds tender masseters bilaterally — a common accompaniment.
The plan follows the reasoning: education (no wide yawns, soft diet, chew bilaterally), moist heat and a short course of NSAIDs, a stabilisation splint if muscle pain dominates, and reassurance that most such episodes improve over weeks to months as the joint adapts; imaging is reserved for failure to progress, trauma, or suspicion of arthritis or ankylosis. Diagnosis here is clinical — MRI is not routine.
High-yield viva angles
Examiners return to the same five questions. "Which muscle of mastication cannot be palpated?" — the lateral pterygoid, deep and medial to the ramus; attempts behind the maxillary tuberosity are unreliable and painful. "Click or crepitus?" — a click is a single sharp sound reflecting disc reduction; crepitus is grating reflecting degenerative change, mapping onto internal derangement versus osteoarthritis. "Deviation or deflection?" — deviation corrects at maximum opening, deflection persists (restricted translation). "Why measure both lateral excursions?" — because the working side condyle rotates while the balancing side translates, so restriction is exposed opposite the direction of movement. "When do you image the TMJ?" — when history suggests trauma, progressive limitation, systemic arthritis, or when surgery is considered.
Frequently asked questions
What are the normal mandibular movement values?
Maximum interincisal opening of 35–55 mm, lateral excursions of 8–12 mm to each side, and protrusion of roughly 6–10 mm; the three-finger test screens opening quickly.
What does a reciprocal click indicate?
Disc displacement with reduction — the disc sits anteriorly at rest and pops back onto the condyle during translation, producing a click on opening and often a second, softer click near closure.
What is the difference between deviation and deflection on opening?
Deviation corrects at maximum opening; deflection persists and indicates restricted condylar translation, as in closed lock or ankylosis.
Why can the lateral pterygoid not be palpated clinically?
It lies deeply, medial to the ramus and coronoid process, and cannot be reached or distinguished reliably by finger palpation; its role is inferred from provocation tests and imaging.
Which imaging modality best shows the articular disc?
MRI, which demonstrates disc position, form and fluid directly; CBCT and plain views show bony contours, sclerosis and ankylosis but not soft tissue.