Twenty-six patients with a sudden-onset of persistent limited mouth opening and with MRI signs of articular discs fixed to the glenoid fossa were studied. After unsuccessful non-surgical treatment, arthroscopy with sodium hyaluronate infusion was performed in 16 joints. Follow-up ranged from 24 to 60 months (mean: 30.3 months). All patients were clinically assessed preoperatively, and at 1, 3, 6, 9, 12, 18 and 24 months postoperatively. The clinical variables analysed were: joint pain using a visual analogue scale (VAS) (1-15), joint noises (clicking, crepitus or none), history of locking, duration of the symptoms, maximal interincisal opening (MIO), maximal protrusive movement (MP) and maximal contra-lateral movement (ML). MRI images were obtained preoperatively to analyse the morphological and dynamic characteristics of the temporomandibular joint. Eight of the patients who refused to undergo arthroscopy were treated with arthrocentesis. These patients were studied following the same criteria as stated above. Mean age of the group was 24.3 years (16-35 years). 20 patients were female and 6 male. The preop-MRI examination revealed a normal disc position in 16 joints and an anteriorly displaced disc in 10 cases. All of the discs were fixed to the glenoid fossa preventing an anterior translation of the condylar head. After non-surgical treatment only two patients improved while all the other patients showed a severe decrease in the MIO (mean 23.3 +/- 2.2 mm), LM (3.8 +/- 1.4) and a high pain level (9.7 scale). Sixteen patients underwent arthroscopy. A significant reduction in pain was noted after arthroscopy. Furthermore, a significant increase in MMO and LM was demonstrated postoperatively. Arthroscopic findings included the presence of adherences and synovitis. Eight patients who refused arthroscopy were treated with TMJ arthrocentesis. All such patients improved their symptoms postoperatively. In conclusion both TMJ arthroscopy and arthrocentesis give good results upon treating patients with anchored disc phenomenon (ADP).