objective: The purpose of this study is to evaluate the therapeutic effect of the combination of Hyaluronic acid and Corticosteroids in treatment of Temporomandibular joint disorder following Temporomandibular arthrocenthesis using single needle technique.   materials   and  methods:   12  young  females  that  have  been  diagnosed  for  internal derangement of the Temporomandibular joint, were divided into two groups where the first group (Study group) were treated by a combination of Hyaluronic acid and Corticosteroids following TMJ arthrocenthesis. While the second group (Control group) were treated only by Corticosteroids.   All procedures were performed using single needle technique and took place at the outpatient clinic of the Oral and Maxillofacial Department, Faculty of Oral and Dental Medicine, Cairo University.   results: The study showed a remarkable decrease in pain sensation and increase in range of mouth opening in the majority of the cases. conclusion: •  Single needle arthrocenthesis is an effective technique for treatment of internal derangement of the TMJ. •  The mix of hyaluronic acid and corticosteroid did not show any significant difference whenMN compared to the injection of corticosteroids alone in mouth opening and VAS score. •   Psychological stresses have a negative effect on temporomandibular condition, and the effectiveness of the treatment procedure.