Radiologic manifestations of rheumatic joint diseases in the plain radiograph

In the assessment of radiologic manifestations of joint diseases, rheumatoid arthritis (RA) is the disease to which all others are compared. Knowledge of its characteristics form the basis of the other conditions. To understand the changes seen on the plain radiograph, it is essential to understand its pathophysiology first so that the manifestations of each disease can be appreciated more fully. Due to space constraint, I shall only discuss the main forms of rheumatic joint disease. Other examples of erosive arthropathies, although not rheumatic in origin, will also be included as they form part of the differential diagnosis of an erosive arthropathy, eg gout and psoriasis.