Although osteoarthritis (OA) generally is considered a disorder of mechanical origin, the common occurrence of chronic mononuclear cell infiltrates in the synovium in conjunction with immunofluorescent evidence for immune-reactant products in cartilage of surgical case specimens (knees, hips, and peripheral joints) has suggested the local involvement of immune processes in the arthritis. Further, the findings of polyarthropathy in the majority of these cases have indicated the propensity for a systemic disorder. Wide variations were noted in both synovial and cartilage immune changes, quite different to those found in rheumatoid arthritis, along with the frequent asymptomatology of the many joints involved. These features, with and without other causative factors, suggest that immune reactions of local and/or systemic origin occur at times in a population at risk for joint degradation.
Professor of Surgery, Chairman of the Clinical Mechanics Group, Department of Surgery, Division of Orthopaedics, Queen's University, Kingston, Ontario, Canada.