Rheumatoid arthritis is a systemic disease that affects multiple joints in the body. Unlike osteoarthritis, which is due to age and wear, rheumatoid arthritis is the result of a disease process throughout the entire body. As a rule, multiple rather than single joints are affected.
Rheumatoid arthritis usually develops between ages 30 and 60 years, but can also present earlier as juvenile arthritis in childhood. Women are more than twice as likely to have the disease as men. There may be a genetic predisposition to getting the disease. Some evidence suggests that rheumatoid arthritis may be an autoimmune phenomenon, but it is unclear as to what triggers the immune response.
The source of the disease is the synovium, the lining tissue of the joint. In a healthy joint, synovium provides lubricant and nutrition to the surrounding tissues. In rheumatoid arthritis, the synovium becomes inflamed and proliferates. The resulting tissue layer is called pannus. Pannus invades the joint surfaces and causes destruction of the cartilage and underlying bone. Inflammatory factor in the synovial fluid may also damage the cartilage.
The diagnosis of rheumatoid arthritis is based largely on clinical factors, but blood tests may also be positive. The rheumatoid factor, an antibody found in blood, is present in most patients with rheumatoid arthritis. The erythrocyte sedimentation rate (ESR) is a less specific test that is often elevated in RA.
The American College of Rheumatology lists seven criteria for the diagnosis of rheumatoid arthritis. Four of these have to be positive in order to confirm the diagnosis. The seven criteria include:
- Morning stiffness
- Arthritis in at least three joints
- Arthritis in the hands
- Joint involvement on both sides of the body
- Positive rheumatoid factor
- Rheumatoid nodules
- X-ray changes consistent with rheumatoid arthritis
Joints with rheumatoid arthritis are warm, swollen, and sometimes contracted. Other clinical features include rheumatoid nodules beneath the skin and tenosynovitis or thickening of the tissue that covers tendons.
The hip is one of many joints in the body that can be affected by RA. Like OA, the onset is gradual. The main symptoms are pain, stiffness, loss of motion, and limping. Usually the diagnosis of rheumatoid arthritis is known to the patient by the time symptoms present in the hip.
The surgical treatment for RA is the same as for OA. If the joint is destroyed total hip replacement is required.
Rheumatoid bone is often osteoporotic and of poor quality. This may affect the choice of components and the type of fixation. If the bone is very soft it may not be possible to press fit components and cement may be required. Patients with rheumatoid arthritis are not candidates for resurfacing because of the risk of bone collapse and failure.