OBJECTIVES: To compare treatment with local anaesthetics and local anaesthetics and lavage in patients with temporomandibular joint (TMJ) pain and reduced mouth opening in a randomized controlled trial. METHODS: Forty-one women and four men (mean age 35 years) participated. All patients had had TMJ pain för more than 3 months, had reduced mouth opening capacity, and had non-reducin disc displacement confirmed by magnetic resonance imaging. The patient were randomized to treatment with extra-articular local anaesthetics alone (control) or with extra-articular local anaesthetics and lavage (treatment). All patients were examined at basline and at 1 and 3 months by an examiner blind to treatment. Successful treatment was determined as 30% or more pain reduction on a 100-mm visual analog scale (VAS). RESULTS: At baseline, mean pain intensity (VAS) on movement of the TMJ was 58 among the controls and 61 in the treatment group. At the 3-month folow-up, treatment was considered succesful in 76% of the controls and 50% of the treatment group. Mouth opening capacity without assistance was 34 mm and 33 mm at baseline and 43 mm and 38 mm after 3 months among the controls and in the treatment group, respectively. These differences between groups in median pain intesity, successful treatment outcome, and mouth opening capacity with assistance were nonsignificant. CONLUSIONS: Use of lavage to supplement extra-articular local anaesthetic treatment of painful reduced mouth opening at non-reducing discs does not appear to improve treatment outcome.