Objectives: Temporomandibular joint (TMJ) arthrocentesis and lavage, first described in the North American literature in 1991, is a simplified method used for the treatment of severe, limited mouth opening. The purpose of this study is to evaluate the efficacy of this technique as a treatment for closed lock of the TMJ.Design: Forty-six patients with persistent closed lock of the TMJ of acute onset were treated by TMJ arthrocentesis and lavage with manipulation in an out-patient setting. Clinical data was collected in the form of visual analogue scales for pain and chewing ability, and measurements of maximum mandibular opening before and after treatment.Results: On follow-up ranging from 6 to 30 months, jaw opening and mandibular function had significantly improved (p < 0.001), and pain had substantially decreased in all but one patient as a result of this procedure.Conclusion: TMJ arthrocentesis and lavage is recommended as a simple alternative to more invasive TMJ procedures as an effective technique for the treatment of acute persistent closed lock of the TMJ.