Unexpected difficult intubation in a patient with normal airway on assessment.

Routine preoperative assessment of the patient's airway includes an assessment of mouth opening and a grading of the view according to the Mallampati scale. This is carried out with the patient sitting and actively opening the mouth without phonation. This case report illustrates that the temporomandibular joint is a complex joint and that certain pathologies may prevent passive depression of the mandible after induction of anaesthesia.