The radiology of rheumatoid arthritis.

Rheumatoid arthritis is a connective tissue disorder of unknown etiology that can involve any synovial-lined joint in the body. The most frequently involved joints are the small joints of the hands and feet, the wrists, knees and elbows, and the glenohumeral and acromioclavicular joints. The radiographic hallmarks of rheumatoid arthritis are swelling of the soft tissue, osteoporosis, narrowing of the joint spaces and marginal erosions. The unique combination of osteoporosis, marginal erosions and relatively minimal reactive bone formation help distinguish rheumatoid arthritis from other inflammatory arthritides.