Temporomandibular joint (TMJ) dislocation
Introduction and scope
Temporomandibular joint (TMJ) dislocation is displacement of the mandibular condyle out of its fossa. Bilateral anterior dislocations are by far the commonest presentation (≈90%).
Emergency clinicians are expected to recognise TMJ dislocation, provide initial analgesia, attempt closed reduction for uncomplicated anterior dislocations where competent and equipped to do so, and arrange imaging and specialist follow‑up.
Complex or non‑anterior dislocations, suspected associated fracture, neurovascular compromise or failed closed reduction require urgent maxillofacial/ENT input (RCEM; NICE).
Anatomy - key points for assessment and reduction
- The TMJ is a synovial compound joint with an intervening fibrocartilage disc dividing it into upper and lower compartments.
- The lateral pterygoid favours anterior translation of the condyle and is particularly relevant to anterior dislocations.
- The masseter and medial pterygoid contribute to closing forces and to muscle spasm/locking.
- Ligaments and the capsule stabilise the joint; collagen disorders (e.g. Ehlers-Danlos, Marfan) increase risk of atraumatic dislocation.
Mechanisms and risk factors
- Traumatic: direct blow to an open mouth (assault, fall, road traffic collision).
- Atraumatic/excessive mouth opening: yawning, laughing, shouting, large bites, dental or ENT procedures.
- Predisposing factors: prior dislocations, poor dentition, connective tissue laxity, muscle dysfunction.