Introduction: TMJ Internal Derangement is a common form of temporomandibular joint disorder. Almost 80% of adult symptomatic patients with TMD have some form of ID. Temporomandibular joint arthrocentesis consists of lavage of upper joint space of TMJ done with no direct vision, aiming primarily to remove necrotic tissue, blood and pain mediators from the joint. One of these therapeutic substances is hyaluronic acid; which is a polysaccharide of the family of glycosaminoglycans, which can be found in many extracellular tissues, including synovial fluid and cartilage. Simvastatins are group of drugs which have good results in regeneration of degenerated TMJ.Aim: This study aimed to evaluate the intra-articular injection of simvastatin versus sodium hyaluronate following arthrocentesis for management of internal derangement (ID) of the temporomandibular joint(TMJ). Patients and methods: Thirty patients with internal TMJ derangement were included in this study. All patients were subjected to preoperative clinical examination and preoperative magnetic resonance imaging (MRI) for the affected joints. Arthrocentesis was performed firstly for the affected joints in all patients followed by intra-articular injection of 1ml. simvastatin twice a month (in group I) and sodium hyaluronate twice a month ( in group II).Clinical follow up were done at 24 hours post-operatively, one week, one month,and six months. Then, after six months MRI was repeated to compare with preoperative images. Results: Better results were recorded with simvastatin group in comparison to sodium hyaluronate group; at 1 week, 1 month,and six months intervals; which was superior to arthrocentesis followed by sodium hyaluronate intra-articular injection. Patients in group I showed better MRI findings in comparison to group II where the position of the disc was almost returned to its normal anatomical position. Conclusion: Arthrocentesis followed by simvastatin intra-articular injection was superior to the combination of arthrocentesis and sodium hyaluronate intra-articular injection for management of TMJ internal derangements symptoms.