Rheumatoid arthritis: a practical guide to state-of-the-art imaging, image interpretation, and clinical implications.

Rheumatoid arthritis (RA) is a chronic systemic disease of unknown origin that predominantly involves synovial tissue. RA affects 0.5%-1.0% of the global population, with females affected more frequently than males. Early diagnosis and initiation of proper therapy help modify the course of the disease and reduce the degree of severe late sequelae. Radiology plays a key role in diagnosis and management of RA. Currently, magnetic resonance imaging is the best imaging modality because it depicts soft-tissue changes and damage to cartilage and bone even better and at an earlier stage than does computed tomography. Ultrasound and conventional radiography are more readily available but cannot show the entire spectrum of the disease. Diagnosis and differential diagnosis are achieved by identifying certain radiologic parameters, which are also used for grading purposes. The disease does not follow a linear course, especially with the early initiation of potent therapy. Knowledge of the imaging findings enables the radiologist to accurately select the most helpful imaging technique. Familiarity with the pathophysiologic mechanisms of RA, the imaging findings, and the grading systems and a basic knowledge of therapeutic regimens are prerequisites for a tailored diagnostic approach by the radiologist. (c) RSNA, 2005.