The Puzzle of Generalized Osteoarthritis (OA) — Is OA a Systemic Enthesopathy?

Abstract

Osteoarthritis (OA) is a common condition that has a major influence on patients’ health-related quality of life. Unfortunately, the riddle concerning the pathogenesis of the disease is still not solved. Generally, we believe that OA is a failure of the whole joint caused by a combination of systemic risk factors and local biomechanical factors1,2. Hand OA is frequent in persons with OA in the larger joints, and may represent a marker of a generalized susceptibility to OA. Kellgren and Moore suggested the concept of generalized OA in the early 1950s3, and numerous later studies have confirmed an association between hand and knee OA and to a lesser extent hip and spine OA4,5,6. Recently, the association was confirmed with modern imaging techniques demonstrating an association between radiographic joint space narrowing in the finger joints and reduced knee cartilage thickness, and between osteophytes in the finger joints and radiographic knee OA7. Although there is ample evidence of an association between hand and knee OA, there is still no consensus about the definition of generalized OA8. The underlying mechanisms beyond this association are not fully understood, although genetic, hormonal, nutritional, neurological, and autoimmune mechanisms have been suggested. Further, one cannot rule out that the observed association is due to common environmental risk factors for hand and knee OA. In this issue of The Journal , Gibson, et al explore the concept of generalized OA and ask whether the disease is related to a systemic enthesopathy9. Entheses are defined as the insertion sites of tendons, ligaments, fascia, or the articular capsule into bone10. The term enthesopathy refers to any pathological involvement of the entheses, including inflammatory, metabolic, traumatic, or degenerative processes. Hence, enthesopathy is … Address correspondence to Dr. Haugen. E-mail: ida.haugen{at}diakonsyk.no