TMJ Internal Derangement

Temporomandibular joint internal derangement is an abnormal relationship between the articular disc and the condyle, fossa and eminence. The disc is usually displaced forward, with or without reduction on mouth opening, and the condition ranges from painless clicking to locking and degenerative change.

It is the commonest structural disorder of the joint and is more frequent in women of 20 to 40 years. Clicking affects roughly a third of the population, and only a minority have pain or limitation that needs treatment.

Pathophysiology. Laxity or elongation of the discal ligaments, a change in disc shape, trauma, parafunction or hypermobility allow the disc to slip off the head of the condyle.

The disc is then recaptured on opening, producing a click (with reduction), or stays displaced and blocks translation of the condyle (without reduction), producing a closed lock. Chronic displacement can lead to perforation of the disc and degenerative joint disease.

Joint clicking or popping on opening and closing, reciprocal clicking, deviation of the jaw to the affected side during opening that corrects, pain on movement or chewing, intermittent locking, and limited opening with deviation to the affected side when the disc does not reduce.

A closed lock gives an abrupt limitation of opening to about 25 to 30 mm with no click. Ask about onset, trauma, parafunction, previous locking, and effect on eating.

Acute lock after trauma, fever with joint swelling, or a sudden open bite needs assessment for fracture, dislocation or septic arthritis.

• Clinical examination: opening range in millimetres, path of opening, click timing (opening, closing or reciprocal), end range stiffness, joint and muscle tenderness, and the effect of manual manipulation.
• MRI of both joints in closed and open mouth positions: shows the disc position and shape, effusion and bone change. This is the reference test for disc position and is needed for surgery planning and uncertain cases.
• Cone beam CT for bone change, and panoramic radiograph as a screen.
• Exclude myofascial pain, arthritis and other causes of locking.
• Joint aspiration for septic or inflammatory arthritis when there is effusion with fever.

Differential diagnosis.

• Myofascial pain and masticatory muscle disorder
• Osteoarthritis of the joint
• Inflammatory arthritis
• Joint dislocation (open lock)
• Coronoid hyperplasia and trismus from other causes
• Condylar fracture or resorption
• Tumour of the joint or parotid

• Painless clicking without locking or pain needs reassurance and no active treatment.
• Conservative care first for painful or locking joints: soft diet, avoiding wide opening, heat or cold, jaw exercises and physiotherapy, behavioural treatment of parafunction, and cognitive support.
• Stabilisation splint worn at night, or an anterior repositioning splint for a short period in selected cases (a few weeks only, to avoid occlusal change).
• Analgesia: ibuprofen 400 mg three times daily with food, or naproxen 250 to 500 mg twice daily with food, for 2 to 4 weeks, with a proton pump inhibitor in people at risk of ulcer. Avoid NSAIDs in renal impairment, peptic ulcer and anticoagulation. Paracetamol 1 g every 6 hours (maximum 4 g daily).
• Acute closed lock: manual manipulation under local anaesthetic or sedation to unlock, within the first few weeks, followed by a splint and exercises. If not successful, arthrocentesis with lavage of 100 to 300 mL of sterile saline or lactated Ringer solution, with or without hyaluronic acid 1 mL injection.
• Persistent pain or limited opening after conservative treatment and arthrocentesis: arthroscopy, or open surgery (discoplasty, disc plication or repositioning, disc removal with replacement) for refractory cases.
• Intra-articular corticosteroid (triamcinolone acetonide 10 mg/mL, 0.5 to 1 mL) is used sparingly, at most 1 or 2 injections a year.

Special groups. Children and adolescents with internal derangement need careful assessment for juvenile arthritis and growth effects, with a conservative approach.

Monitoring. Review at 4 to 6 weeks and 3 months for pain, mouth opening and click, then every 6 to 12 months. Repeat MRI if symptoms change or surgery is planned.

Referral and escalation. Refer to oral and maxillofacial surgery or an orofacial pain clinic for locking, persistent pain or failed conservative care. Urgent referral for trauma, fever with joint swelling or an acute change in occlusion.