What are some common imaging features of RA?
Soft tissue swelling is often present and periarticular in location, usually due to an underlying joint effusion or tenosynovitis. Early in the disease process, this may be the only finding observed. Bone mineral density is typically decreased, particularly within juxtaarticular locations, which is often exacerbated by corticosteroid therapy. Joint space narrowing tends to involve the joint spaces symmetrically. Bony erosions may be present, typically along the margins of the articular surface (i.e., marginal erosions), affecting the “bare areas” of the bones first ( Figure 49-2 ). These areas lack overlying hyaline cartilage, leaving the exposed bone susceptible to the destructive inflammatory process. Overall, the disease process tends to be symmetric in the body. However, asymmetry may be present in early phases of the disease process.