Rheumatoid Arthritis (RA)

In joints affected by RA, inflammatory cytokines produced by activated T cells and macrophages increase the receptor activator of nuclear factor kappa-Β ligand (RANKL) expression in synovial fibroblasts and induce osteoclasts, which results in bone destruction, such as bone erosion and juxtaarticular osteoporosis. Inflammatory cytokines also induce the production of extracellular matrix proteases (MMP-3 and ADAMTS-4). MMP-3 degrades proteoglycans and collagen, whereas ADAMTS-4 degrades aggrecan, resulting in cartilage destruction. Typical radiographic findings in knees with RA include bone erosion and atrophy, joint surface destruction, and joint space narrowing. In knees with RA having joint destruction, secondary osteoarthritis (OA) changes, such as periarticular osteophyte formation and subchondral bone sclerosis, may be observed when inflammation is adequately controlled.