Figure 1.

Schematic representation of inflammation process in osteoarthritis. OA is defined by the progressive breakdown of articular cartilage and subchondral bone, and also low-grade inflammation. Following joint injury, cartilage tissue damage causes the production of damage-associated molecular patterns (DAMPs), which include cartilage extracellular matrix (ECM) breakdown products and intracellular alarmins that signal pattern recognition receptors on synovial macrophages, fibroblasts, T cells, or chondrocytes to induce the local release of inflammatory mediators. These activated cells will produce inflammatory factors such as cytokines, chemokines, and catabolic enzymes, either directly or indirectly by inducing proteolytic enzymes which will accelerate cartilage destruction in the progressing osteoarthritis.