Background: The turning point in the treatment of TMJ internal derangement was the introduction of TMJ arthrocentesis. To enhance the outcome of arthrocentesis, post operative intra-articular injection of various substances were used. The aim of this study was to evaluate the clinical response to single needle arthrocentesis with intra-articular injection of tenoxicam in relation to the improvement in VAS, MMO, lateral movement, and joint sound in patient with TMJ ID.Patient and methods: Twelve patients with chronic unilateral ID were selected, they were ten females and two males and they don’t respond to conservative treatment. Single needle arthrocentesis was performed followed with intra-articular injection of 1ml of tenoxicam at the end of the procedure. Another injection of 1ml of tenoxicam was done at the 7-14 days post arthrocentesis.Results: In the current study there was non-significant decrease in mean of VAS in preoperative- one week post arthrocentesis and one week post second injection period. There was significant difference in mean of VAS, MMO, right lateral movement, and left lateral movement through the whole study period (preoperative- 12 weeks).There was no significant difference in mean of joint sound through the whole study period (preoperative- 12 weeks). Conclusion: Intra-articular injection of tenoxicam at the end of arthrocentesis procedure show non-significant effect neither on the postoperative pain nor on its clinical outcome.