TMJ Closed Lock

What is it?

Anteriorly displaced disc fails to reduce, mechanically blocking condylar translation and limiting opening.

Commonly affected: Unilateral anterior/anteromedial disc displacement without reduction

How it develops

1. Chronic DisplacementLong-standing anterior displacement
2. Disc DeformationDisc folds or adheres
3. Failure to ReduceCondyle cannot slide under disc
4. Mechanical LockLimited opening (<35 mm), ipsilateral deflection

Symptoms

• Limited opening (<35 mm)Opens only 2 fingerbreadths
• Unilateral jaw painPain at affected joint
• Chewing difficultyCannot chew hard food
• Deflection to affected sideJaw deflects to affected side
• Loss of clickingPrevious click disappears (preceding lock)

How it is examined

• Max opening <35 mmFinger or ruler measurement
• Deflection to affected sideDeflects to affected side without midline return
• Joint tendernessLateral pole tenderness
• Restricted lateral excursionLimited contralateral excursion

Imaging

Panoramic usually normal; chronic cases may show bony change.

• Usually normal bone
• Possible joint space change
• OA changes in chronic cases

MRI is gold standard — disc remains anterior even on opening.

• Anterior disc at closed mouth
• Disc stays anterior on opening (no reduction)
• Disc deformation (folded)
• Possible effusion/marrow edema

When surgery is considered

Failure of 3–6 months conservative care, persistent pain/limitation

Procedures that may be discussed

• Arthroscopic lysis/lavage
• Arthroplasty
• Disc repositioning (discopexy)

Outlook

70–80% recover with conservative care; chronic cases may progress to OA.