Participants are randomly assigned to receive three injections, each a week apart, of either Synvisc or placebo (a salt-water solution) into the affected joint. Before the first injection, a sample of synovial fluid is collected from the joint by needle aspiration for laboratory analysis. Patients return for follow-up visits 3, 6, and 12 months after the last treatment for a clinical examination of the jaw joint and review of jaw joint symptoms. A second aspiration is requested at the 3-month visit, but is not mandatory. All injections and aspirations are done after anesthetizing the overlying skin and joint capsule to minimize pain or discomfort. Participants record their daily use of pain relief medication throughout the study.