This research protocol will recruit patients with arthritis and related conditions for the purpose of screening patients for treatment protocols, and evaluating the natural history of arthritis and related conditions. Patients will be evaluated clinically, radiographically and serologically, and standardized data will be uniformly collected on all patients. Additional imaging using sensitive MRI methods will be obtained in some patients. The collected blood and tissue will be utilized for laboratory studies to continue research on the pathogenic mechanisms of rheumatoid arthritis and related autoimmune joint diseases. Data from the history and physical examination as well as several disability questionnaires in the adult and pediatric population will be used to phenotypically characterize these patients and assess outcome and functional status. Any medical care recommended or provided to the patients will be consistent with routine standards of practice and provided in consultation with the patient's referring physician.