Objective: To compare treatment with local anaesthetics and local anaesthetics in combination with lavage in patients with temporomandibular joint (TMJ) pain and reduced mouth opening in a randomized controlled trial. Material and methods: Forty-one women and four men (mean age of 35 years) participated. All patients had had TMJ pain for more than 3 months, had reduced mouth opening capacity, and had non-reducing disc displacement confirmed by magnetic resonance imaging. The patients were randomized to treatment with extra-articular local anaesthetic alone (control) or with extra-articular local anaesthetic in combination with lavage (treatment). All patients were examined at baseline 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 analog scale (VAS). Results: At baseline, mean pain intensity (VAS) of the TMJ during mandibular movements was rated 58 among the controls and 61 in the treatment group. At the 3 months follow-up, treatment was considered successful in 76% of the controls and 50% of the treatment group. Mouth opening capacity was 34 mm and 33 mm at baseline and 43mm and 38 mm after 3 months among the controls and in the treatment group, respectively. These differences between groups in pain intensity (VAS), successful treatment outcome (≥ 30%), and mouth opening capacity (mm) were non-significant between groups. Conclusion: Use of lavage to supplement extra-articular local anesthetic treatment of painful reduced mouth opening at non-reducing dics does not appear to improve treatment outcome. only.