The proposed clinical trial will evaluate the effects of high molecular weight hylan (Synvisc) injection in comparison with control treatment (saline injection) for osteoarthritis (OA) affecting the temporomandibular joint (TMJ). Patients with TMJ OA of at least three-month duration and who have not responded to conservative treatments will be included. Patients will be randomly assigned to either high molecular hylan injection or control. At baseline and follow up visits, clinical outcome measures will be assessed such as pain and range of motion. Positive findings in clinical outcome measures will provide evidence for the clinical utility of Synvisc in patients with painful TMJ OA. In addition to clinical outcome measures, a sample of synovial fluid from the affected joint will be obtained at the baseline visit and at 12 week follow up, and levels of tumor necrosis factor alpha (TNF alpha), Matrix metalloproteinase (MMP) and Tissue inhibitor of metalloproteinase (TIMP) will be analyzed. By studying the synovial fluid levels of TNF alpha, MMP and TIMP, we will assess the effects of viscosupplementation with Synvisc on the local inflammatory process and proteolytic activity in TMJ OA in comparison with control treatment. Positive findings in clinical symptoms and synovial fluid analysis will also provide implications of clinical utility of Synvisc in patients with painful TMJ OA. Furthermore, this analysis of synovial fluid may identify biomarkers associated with OA affecting the TMJ.