This clinical study aimed to radiologically and clinically compare the effect of intra-articular injection of methylprednisolone, sodium hyaluronate or tenoxicam following arthrocentesis with that of arthrocentesis alone in patients with non-reducing disc displacement. A total of 44 patients radiographically diagnosed with non-reducing disc displacement of the temporomandibular joint (TMJ) were randomly divided into four treatment groups, as follows: Group 1, arthrocentesis alone; Group 2, arthrocentesis plus methylprednisolone acetate; Group 3, arthrocentesis plus sodium hyaluronate; Group 4, arthrocentesis plus tenoxicam. Maximum mouth opening (MMO), lateral movement, pain severity and tenderness of TMJ and muscles of mastication on palpation were measured before treatment and at 1 week and 1, 3 and 6 months after treatment. Disc position, presence or absence of disc reduction, level of effusion, joint movement and joint space were also evaluated using magnetic resonance imaging (MRI) before treatment and 6 months after treatment. No significant differences in treatment success were found among the four groups. MRI findings did not vary significantly among the groups, but pre- and post-operative MRI findings varied significantly within all four groups (p<0.001). According to the data from this study, it may be concluded that either arthrocentesis alone or arthrocentesis with methylprednisolone acetate or sodium hyaluronate or tenoxicam intra-articular injections are similarly effective and promising methods in the treatment of TMJ with non-reducing disc displacement.