Anterior Disc Displacement with Reduction

Anterior disc displacement with reduction is a position of the temporomandibular joint disc in front of the condylar head when the mouth is closed, with return of the disc over the condyle on opening, usually with a click. It is the commonest form of disc displacement.

Joint clicking is reported by about a third of adults, though most have no pain or limitation and need no treatment. The condition is more frequent in women in the second to fourth decades.

Pathophysiology. Elongation of the posterior attachment and discal ligaments, a change in disc shape, hypermobility or parafunction allow the disc to slip forward and usually medially.

On opening the condyle moves up onto the posterior band of the disc, producing the opening click. On closing, the disc slides forward again, producing a second click, so the click is reciprocal. Over time, a small proportion progress to displacement without reduction, with pain and degenerative change.

A click or pop in the joint on opening and closing, often with a small deviation of the jaw to the affected side that corrects after the click. Maximum opening is normal, 40 mm or more. Most have no pain. Some have pre-auricular pain, muscle pain or intermittent catching.

Ask about locking episodes, trauma, bruxism, gum chewing, previous orthodontic or dental work, and joint hypermobility. The click moves earlier in opening as the disc becomes less stable and later as the disc becomes more displaced.

A sudden loss of the click with limited opening suggests that the disc has stopped reducing and needs prompt review.

• Clinical diagnosis: reproducible reciprocal click on opening and closing, normal opening range, and a deviation that corrects. Auscultation or palpation confirms the click.
• MRI in closed and open mouth positions when the diagnosis is uncertain, symptoms are persistent, or surgery is considered. It shows the disc anterior to the condyle at closure and normally positioned on opening, and may show effusion or bone change.
• Cone beam CT for bone change, and panoramic radiograph as a screen.
• Exclude other causes of clicks and pain: osteoarthritis, myofascial pain, loose bodies, and hypermobility.

Differential diagnosis.

• Anterior disc displacement without reduction
• Osteoarthritis of the joint
• Myofascial pain of the masticatory muscles
• Condylar hypermobility and subluxation
• Loose body or synovial chondromatosis
• Muscle clicks and occlusal interferences
• Inflammatory arthritis

• Reassurance and explanation for painless clicking with normal function. No active treatment is needed, and the click may persist for years.
• Self-care when symptomatic: soft diet for 1 to 2 weeks, avoiding wide opening, gum chewing and nail biting, heat for 15 to 20 minutes, and gentle jaw exercises. Reduce parafunction by behavioural measures.
• Analgesia for painful episodes: ibuprofen 400 mg orally three times daily with food for 1 to 2 weeks, or naproxen 250 to 500 mg twice daily with food, 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).
• Stabilisation splint worn at night for 3 to 6 months for pain or frequent locking. An anterior repositioning splint is used for a few weeks in selected cases, with attention to the risk of a permanent change in the bite.
• Physiotherapy: supervised jaw exercises and posture work.
• Arthrocentesis with lavage of 100 to 300 mL of saline or lactated Ringer solution, with or without hyaluronic acid 1 mL, for persistent pain or catching not responding to conservative care.
• Surgery (disc repositioning or plication) is rarely needed and reserved for refractory disabling cases.

Monitoring. Review at 4 to 6 weeks for pain and function, then at 3 months. Record opening range and click timing, and repeat imaging if locking develops.

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 fever with joint swelling or trauma.