Rheumatoid arthritis is a chronic systemic inflammatory disease that primarily attacks peripheral joints and their surrounding muscles, tendons and ligaments. The autoantibodies to this altered IgG are known as rheumatoid factors. Rheumatoid factors combine with IgG to form immune complexes that deposit in the joints. This creates an inflammatory response that leads to proteolytic enzyme production, which can further damage articular cartilage. The inflammation in the joint inflammation is the main source of pain.
Joint inflammation occurs in four stages.
First, synovitis develops from congestion and edema of the synovial membrane and joint capsule. Second, thickened layers of granulation tissue called pannus develop. Pannus covers and invades cartilage and eventually destroys the joint capsule and bone. Third, fibrous invasion of the pannus and scar formation occludes the joint space. This causes bone deterioration and misalignment.