On MRI of the temporomandibular joint (TMJ), the normal articular disc appears as a biconcave band of low signal on T1 and T2 sequences positioned between the condyle and the articular eminence. Anterior disc displacement without reduction is best diagnosed when:

• A The disc remains anteriorly displaced on both closed-mouth and open-mouth MRI sequences ✓
• B The disc is displaced anteriorly only on closed-mouth views and reduces normally on mouth opening
• C The disc shows T2 hyperintensity indicating perforation
• D Condylar sclerosis and flattening are present on CT

Explanation

Anterior disc displacement without reduction (ADDWR) means the disc remains anterior to the condyle in both closed-mouth and open-mouth positions on MRI — the condyle cannot 'recapture' the disc on opening, producing restricted jaw opening (closed lock). Anterior disc displacement WITH reduction (ADDWR) shows the disc displaced anteriorly on closed-mouth view but returning to normal position over the condyle on open-mouth view, producing a click. T2 signal change indicates disc degeneration, not displacement type. Condylar changes on CT are secondary degenerative findings.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.