TMJ Disorders
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Direct answer
Temporomandibular joint disorders cover a spectrum from the commonest — masticatory muscle disorders and myofascial pain — through disc displacement disorders, degenerative and inflammatory arthritides to ankylosis. Internal derangement follows a recognisable progression: a reciprocal click as the disc reduces on opening, then intermittent locking, then closed lock without reduction, finally crepitus as surfaces degenerate — the sequence formalised in the five Wilkes stages that treatment planning hangs upon. Management is stepped and predominantly reversible: education, physiotherapy, splints and analgesics first, arthrocentesis and arthroscopy next, open surgery rarely.
What you must remember
- Normal parameters to quote: interincisal opening 40-55 mm (worry below about 30-35 mm), lateral excursions about 8-10 mm; measure with a ruler, not by impression.
- Disc displacement with reduction: painless or mildly painful clicking; without reduction: closed lock, opening limited to 25-30 mm, mandible deflecting to the affected side.
- Wilkes staging: I — painless clicking; II — occasional locking with click; III — intermittent lock, restricted opening, no bone change; IV — pain, crepitus, organic bone change; V — gross crepitus, severe restriction, perforation.
- Imaging ladder: orthopantomogram as screen, CT for bone, MRI the definitive test of disc position; the diagnosis is overwhelmingly clinical.
- Reversible therapy first: soft diet, habit awareness, warm fomentation, NSAIDs, physiotherapy, and a full-coverage stabilisation splint at night; anterior repositioning appliances reserved and time-limited.
- Arthrocentesis — lysis and lavage of the upper joint space through two needles — is the first surgical step for Wilkes III-IV, washing out inflammatory mediators and releasing adhesions, with most closed-lock patients improving.
- Higher rungs: arthroscopy with adhesiolysis, disc repositioning, discectomy for end-stage painful joints; alloplastic total joint replacement for end-stage adult disease.
- The TMJ shares innervation with the ear, so earache with a normal ear examination is classic referred TMD pain via the auriculotemporal nerve.
A typical exam case
A 27-year-old woman presents with six months of left preauricular pain, clicking for two years, and a three-week history of the jaw "catching" — twice it would not open beyond two fingers. Examination: opening 31 mm with deflection to the left, a palpable click at 20 mm that disappears on opening through protrusion, tender left masseter and temporalis, no neurological deficit. Staging: recurrent clicking with intermittent locking, near-normal opening — Wilkes stage II to early III, disc displacement with reduction trending towards without. Plan stepwise. Explain the mechanics — the disc is failing to stay on the condyle, and parafunctional clenching is loading it. Prescribe a night stabilisation splint, soft diet, NSAIDs for two weeks, and jaw exercises with warm packs. Review at six weeks. If she locks without reduction — opening stuck near 25 mm, click gone — proceed to MRI, then arthrocentesis of the upper joint space under LA or sedation, followed the same day by aggressive physiotherapy; this single intervention restores acceptable opening in most patients and is the answer expected before any open surgery.
How the exam frames it
Two differentiators separate prepared candidates. First, click versus crepitus: a click is disc reduction — a soft, well-defined sound at a reproducible opening distance; crepitus is grating from surface degeneration — and conflating them collapses the entire staging logic. Second, deflection versus deviation: the mandible deviating to one side and correcting is disc displacement on that side; a straight pull to one side that stays is a harder limit — closed lock on that side, or ankylosis if lifelong. Examiners also enjoy "which splint, when": the stabilisation splint for muscle pain and protection; the anterior repositioning appliance controversially to recapture the disc, time-limited because it causes posterior open bite. And remember myofascial pain outnumber all joint problems — a candidate who jumps to MRI and surgery for bilateral dull ache with trigger points in masseter has misread the question entirely.
Frequently asked questions
What is the Wilkes stage of a joint with recurrent clicking and intermittent locking but normal radiographs?
Stage II — early internal derangement with occasional locking and slight disc deformity, still without structural bone change.
How does closed lock present clinically?
Opening limited to roughly 25-30 mm, deflection of the mandible to the affected side, loss of the previous click, and preauricular pain — disc displacement without reduction.
Which imaging modality best demonstrates disc position?
MRI, which shows disc form, position in opened and closed positions, joint effusion and marrow change; CT defines bony architecture.
What is arthrocentesis and when is it indicated?
Lavage of the upper joint space with two needles to wash out inflammatory mediators and break early adhesions, indicated for Wilkes stage III-IV internal derangement, especially closed lock, before arthroscopy or open surgery.
Why does TMD cause ear symptoms?
The joint and ear share innervation via the auriculotemporal nerve and the tympanic plexus, so referred otalgia with a normal ear examination should prompt TMJ and muscle assessment.
Which TMD is the commonest overall?
Masticatory muscle disorder — myofascial pain — rather than disc or joint disease; it presents as bilateral dull ache with trigger points and full opening.