The TMJ articular disc is a biconcave fibrocartilaginous structure that divides the TMJ into an upper (temporodiscal) and a lower (condylodiscal) joint compartment. The disc is thickest at its anterior and posterior bands and thinnest centrally (the intermediate zone). Anteriorly it is attached to the superior head of the lateral pterygoid muscle; posteriorly the bilaminar zone (retrodiscal tissue) connects it to the posterior capsule and tympanic plate.
The TMJ disc is the structure involved in internal derangement, the most common TMJ disorder. Anterior disc displacement with reduction produces a clicking sound when the condyle recaptures the disc during opening (reciprocal click). Anterior disc displacement without reduction (closed lock) prevents full mouth opening (less than 35 mm) as the displaced disc blocks condylar translation. MRI in the sagittal closed and open mouth positions demonstrates disc position, deformation, and mobility. Initial management is splint therapy and physiotherapy; arthroscopic disc release or open disc repositioning for refractory cases.
Chronic anterior TMJ disc displacement without condylar recapture produces an acute closed lock with sudden inability to open the mouth beyond 25-30 mm, deviation to the ipsilateral side, and loss of the previous click; managed by manipulation under anaesthesia, arthroscopic disc release, or open arthroplasty for long-standing cases.
