OFP EXTRA OSCE Q2 - TMJ Internal Derangement

Worked answers for OFP EXTRA OSCE — Question 2.

Scenario

Victor is a 45-year-old male who presents to your clinic reporting restricted mouth opening and left-sided jaw pain of gradual onset over the past several months. He describes pain with function, particularly during chewing and yawning, along with an intermittent dull ache at rest. He recalls a prior history of left jaw clicking that he noticed had stopped around the time his mouth opening became restricted, which may indicate an internal derangement. On examination you note tenderness on palpation of the left masseter and left preauricular region.

Questions (each 3 marks; total 21 marks)

1. Identify 3 possible aetiologies associated with restricted mouth opening. (3 marks)
2. Based solely on the information provided above, what are the possible diagnoses for this patient? (3 marks)
3. Describe your diagnostic approach and the investigations required to determine the cause of his restricted mouth opening. (3 marks)
4. Name 3 distinct subtypes of internal derangement of the temporomandibular joint (TMJ). (3 marks)
5. For each subtype identified, describe one key diagnostic feature. (3 marks)
6. Outline the management options available for internal derangement of the TMJ. (3 marks)
7. What factors may affect this patient’s overall prognosis? (3 marks)

1. Identify 3 possible aetiologies associated with restricted mouth opening.

• Disc displacement without reduction with limited opening (closed lock) — the displaced disc acts as a mechanical obstruction that blocks condylar translation.
• Masticatory myalgia with protective co-contraction — pain-driven guarding of the muscles of mastication limits opening; characterised by a soft end-feel.
• Degenerative joint disease (osteoarthrosis/osteoarthritis) — structural breakdown of the articular surfaces, typically with crepitus and opening usually <35 mm.

Other accepted causes: arthralgia, and inflammatory disorders (synovitis, capsulitis, retrodiscitis).¹

2. Based solely on the information provided above, what are the possible diagnoses for this patient?

• Primary diagnosis: anterior disc displacement WITHOUT reduction WITH limited opening (closed lock) of the left TMJ.
  • The cessation of the previously noted click occurring at the same time as the new opening restriction is the classic transition from a reducing to a non-reducing disc.
• Concurrent contributors (explaining the masseter and preauricular tenderness):
  • Left masticatory myalgia — tenderness on palpation of the left masseter.
  • Left arthralgia — tenderness of the left preauricular (joint) region plus pain on function and a dull ache at rest.¹

3. Describe your diagnostic approach and the investigations required to determine the cause of his restricted mouth opening.

Clinical examination of the TMJs and masticatory muscles:²

• Visual inspection for facial asymmetry and mandibular deviation on opening.
• Measurement of maximum unassisted and assisted mouth opening (mm), lateral excursion and protrusion.
• Palpation of the TMJs (lateral pole and posterior attachment) and masticatory muscles (masseter, temporalis, medial and lateral pterygoid) for tenderness.
• Palpation/auscultation for joint sounds, characterising timing (opening click, closing click, or crepitus).

Discriminating examination features:¹

• Deviation vs deflection — deviation moves to one side then corrects (reducing disc); deflection moves to one side and stays there (non-reducing/closed lock).
• Soft vs hard end-feel — soft end-feel suggests a muscular cause (can be stretched further); hard end-feel suggests an intracapsular mechanical stop.

Investigations:²

• OPG — baseline assessment of bony joint architecture (limited; cannot show disc position).¹
• MRI of the TMJs — gold standard (~90% accuracy) for disc position, morphology, and joint effusion; closed- vs open-mouth views confirm whether the disc reduces.¹
• CBCT/CT — where bony pathology, condylar resorption, or articular surface change is suspected.
• Serological investigations (ESR, CRP, rheumatoid factor, ANA) if systemic arthritis is a differential.

4. Name 3 distinct subtypes of internal derangement of the temporomandibular joint (TMJ).

From the DC-TMD classification of intracapsular disorders:¹

• Disc displacement with reduction.
• Disc displacement with reduction with intermittent locking.
• Disc displacement without reduction with limited opening (closed lock).

(A fourth recognised subtype is disc displacement without reduction without limited opening.)¹

5. For each subtype identified, describe one key diagnostic feature.

Subtype	Key diagnostic feature
Disc displacement with reduction	Reproducible clicking/popping on opening and/or closing as the disc “reduces”; normal opening with ipsilateral deviation that corrects.
Disc displacement with reduction with intermittent locking	Episodes of intermittent “catching”/locking on a background of clicking; the jaw can be freed by a small movement, restoring normal opening.
Disc displacement without reduction with limited opening (closed lock)	Loss of the prior click plus limited opening (typically <35–40 mm) with uncorrected ipsilateral deflection and restricted contralateral excursion.

All three subtypes and their diagnostic features above follow the DC-TMD classification.¹

6. Outline the management options available for internal derangement of the TMJ.

Management follows a conservative-first then specialist ladder.

Conservative (first-line):¹

• Patient education and reassurance.
• Soft (nutrient-dense) diet and parafunctional habit control (clenching, jaw bracing; avoid gum and wind instruments).
• Thermotherapy and physiotherapy — heat/ice, jaw exercises, “tongue-to-roof” controlled opening to correct deviation.
• Stress management and oral appliances (stabilisation splint) to offload the joint and protect against bruxism.
• Pharmacotherapy — NSAIDs (e.g. ibuprofen 600 mg TDS), topical diclofenac gel, muscle relaxants, TCAs/SSRIs, or Botox.²

Specialist referral and procedures (persistent symptoms, recurrent locking, diagnostic uncertainty, or significant functional limitation):¹

• Custom stabilisation splints.
• Intra-articular corticosteroid injections.
• Arthrocentesis (joint lavage).
• Arthroscopy (adhesiolysis, synovial assessment).
• Open joint surgery (rare) for disc repositioning or repair.

7. What factors may affect this patient’s overall prognosis?

• Severity and chronicity of the disorder at presentation.²¹
• Patient compliance/adherence to self-management.¹
• Psychosocial comorbidities (anxiety, depression, pain catastrophising) and genetic predisposition.²¹
• Degree of structural change on imaging.²
• Coexistence of other chronic overlapping pain conditions (central sensitisation / chronic pain elsewhere).²¹

Footnotes

1. L29 Intracapsular disorders of TMD. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴

2. OFP Mock Formative Q2 - TMJ Disc Displacement and Clicking_integrated — marking key. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷