Rheumatoid arthritis is a lifelong inflammatory disease that can affect all parts of the body, though it typically affects the ankles, knees, wrists and fingers on both sides of the body. Symptoms of this condition are fever, weakness, swelling, pain and deterioration of the affected joints. It also involves periods of unpredictable flare-ups and partial remission. The book "Straight A's in Pathophysiology" explains that rheumatoid arthritis progresses in four stages.

The first stage of rheumatoid arthritis is characterized by a condition called synovitis. There is no severe damage in this stage, but the synovial lining, the lining of the joint, swells. As a result, patients experience pain, redness, warmth, stiffness and inflammation around the affected joints. "Imaging of the Head and Neck," by Mahmood F. Mafee, Galdino E. Valvassori and Minerva Becker, says that osteoporosis is seen in the first stage of rheumatoid arthritis. X-rays may also reveal signs of swollen soft tissues in the joint.

The second stage of rheumatoid arthritis involves the thickening of the synovial lining, or synovium. This happens when the cells of the synovium grow and divide at an accelerated rate. As the synovium grows, it covers the cartilage and can eventually destroy the joint capsule and bone.

The damage done in stage 3 rheumatoid arthritis is quite severe. The inflamed cells of the synovium release enzymes that may digest the bone and cartilage in the joint. This causes deformities, loss of movement, partial dislocations, muscle wasting and pain in the joint. At this point, X-rays will show severe loss of cartilage and erosion around the edges of the joint.

Stage 4 rheumatoid arthritis is the end stage of the disease. The inflammatory process begins to die down, the joint becomes less functional and may become totally immobile. "Exercise Testing and Exercise Prescription for Special Cases: Theoretical Basis and Clinical Application," by James S. Skinner, says that in this stage, changes from the previous stages are observed. "Physiotherapy in Orthopaedics: A Problem-Solving Approach," by Karen Atkinson, Fiona Coutts and Anne-Marie Hassenkamp, explains that irreversible cartilage destruction occurs at this stage.