Our aim was to find out whether pain was better controlled if morphine or tramadol was injected intra-articularly after arthrocentesis with Ringer's lactate in patients with painful temporomandibular joints (TMJ). This placebo-controlled, double-blind study involved 30 patients who had not responded to conservative treatment and who were divided randomly into 3 groups of 10 patients each. All patients had arthrocentesis, and the drugs were given as intra-articular injections immediately after the procedure. One group was give 5% Ringer's lactate 1 ml, the second morphine 1 mg, and the third tramadol 50 mg. Visual analogue scales (VAS) for pain were recorded at maximum mouth opening and at rest before intra-articular injection and after 15 and 30 min; at 1, 2, 3, 8, 12, 24, 36 and 48 h; and at 1, 3, and 6 monthly follow-up. The mean (SD) VAS decreased from 6.90 (1.45) to 2.6 (2.5) in the control group, from 7.30 (1.64) to 1.20 (0.79) in the morphine group (p = 0.005), and from 7.10 (1.73) to 1.50 (1.78) in the tramadol group (p = 0.005). We conclude that morphine given by intra-articular injection after arthrocentesis gives a significant, sustained (6 months) improvement in pain relief compared with simple arthrocentesis alone. The effect was similar with tramadol except that it was shorter lived. (C) 2015 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.