Rheumatoid arthritis is a chronic and progressive inflammatory disease of the joints. It affects approximately 1% of the general population, with incidence being three times higher in women than men. The areas most commonly involved are the metacarpophalangeal joints, the proximal interphalangeal joints, and the feet.
Small-parts ultrasound has become increasingly important for the early diagnosis of rheumatoid arthritis. Clinical findings, including swelling and joint tenderness, can be supported by an ultrasound examination that documents the characteristic pattern of inflammation.
Early stages of disease primarily affect the synovium. Acute synovial inflammation (synovitis) is characterized by increased synovial vascularity (neoangiogenesis) and is regarded as a predictive marker of erosive progression.1,2 The chronic inflammatory process causes synovial proliferation and the development of the aggressive pannus that can undermine articular cartilage and cause irreversible erosions at the osteochondral junction (bare areas). Adjacent structures, such as the capsule, cartilage, ligaments, tendons (Figure 1), and adjacent bone, become involved during the course of the disease.
Synovitis appears to be the best predictive marker of future damage. An early diagnosis of rheumatoid arthritis coupled with an assessment of the extent of pre-erosive inflammatory features is consequently important to a good clinical outcome. New biological, disease-modifying antirheumatic drugs can suppress disease activity and joint destruction. Therapeutic advances such as this put pressure on diagnostic imaging to provide an accurate and prompt diagnosis, as well as adequate monitoring of disease progression.
Conventional radiography should be performed initially in each patient to assess the baseline joint status. This will permit further rheumatic changes to be evaluated in context and allow confirmation of a suspected diagnosis. We should keep in mind, however, that radiography has lower diagnostic value than ultrasound and MRI for the determination of acute inflammation. It will depict only indirect signs of cartilage loss, such as joint space narrowing and bony erosions due to previous destructive synovial inflammatory activity. A further drawback is length of time required for erosions to become visible on radiography. Signs of destruction seen on ultrasound and MRI may not become visible on plain film x-ray images for up to a year.