Rheumatoid Arthritis: Other Causes of Joint Pain

Topic Overview

Many diseases in addition to rheumatoid arthritis may cause joint pain.

• Osteoarthritis: The illness most often confused with rheumatoid arthritis is osteoarthritis. Although these diseases share the symptom of severe joint pain with reduced mobility, they have distinct causes and treatments.
  • Osteoarthritis is caused by wear and tear over time or by injury to the joints, which results in the degeneration of the hard, smooth layer of cartilage that normally covers and protects the ends of the bones.
  • Unlike rheumatoid arthritis, osteoarthritis is not usually associated with activation of the immune system, so people with osteoarthritis do not have the systemic symptoms of rheumatoid arthritis such as fever and fatigue that are caused by the release of chemical messengers from immune cells.
  • Patients with osteoarthritis may develop bony enlargements of the affected joints, but they do not have the signs of inflammation around the joints, such as warmth, redness, and soft swelling.
  • Because rheumatoid arthritis is a systemic disease, which means that it spreads freely through the body as it follows the flow of immune cells in the bloodstream, it most commonly affects joints symmetrically on both sides of the body. By contrast, osteoarthritis is often more localized, especially when a joint becomes arthritic secondary to injury, and therefore osteoarthritis is more likely if the arthritis is on only one side of the body, or asymmetric.
  • Different joints are preferentially affected by the two diseases. Rheumatoid arthritis is most common in the small joints, such as the knuckles, wrists, elbows, ankles, toes, shoulders, and neck. Osteoarthritis very commonly affects the large weight-bearing joints in the hips and knees, as well as the thumb and the joints closest to the tips of the fingers.
• Other joint diseases: Like rheumatoid arthritis, other autoimmune diseases can also attack the tissues of the joint.
  • Lupus: Lupus most often occurs in young women, and it affects organs all over the body. Other symptoms of lupus include pleurisy, butterfly facial rash, sun-sensitive rashes, hair loss, oral ulcers, rash, and seizures.
  • Sjögren's syndrome: Symptoms include dry eyes and dry mouth (sicca syndrome) and sometimes joint pain.
  • Sarcoidosis, which can also affect the lungs and other organs throughout the body
  • Some forms of polymyositis, an autoimmune disorder affecting the muscles
  • A class of diseases called the spondyloarthropathies, including reactive arthritis, psoriatic arthritis, and ankylosing spondylitis
• Infections: If bacteria or viruses get into the joint space, they will initiate a local immune response leading to swelling of the joint and pain. Bacterial infections of joints will cause severe pain and swelling only in the single joint, because the infection tends to be localized. Viruses-especially hepatitis B and C, HIV, and parvovirus-can affect single joints but also can cause a generalized reaction that affects joints all over the body. Infection-associated arthritis generally resolves when the infection is treated.
• Gout: Uric acid crystals that form in gout can get into the joint and cause periodic acute joint pain and swelling. When gout is treated with medicines, the arthritis that it causes goes away.
• Pseudogout: Calcium pyrophosphate crystals get into the joint and cause acute pain and swelling. When treated with medicines, the pain disappears.
• Polymyalgia rheumatica: This is seen in people older than 50, with a usually abrupt onset of pain and stiffness in the neck, both hips, shoulders, and buttocks.
• Fibromyalgia: The fibromyalgia syndrome can cause joint pain but can be distinguished from rheumatoid arthritis by the predominance of pain and tender points in soft tissue and the absence of swollen joints. Fibromyalgia is a poorly understood disorder in which it appears that the body's perception of normal stimuli is altered so that widespread pain occurs, some of which is in the joints.

Examples of causes of joint pain by distribution of affected joints

Type of arthritis	Affects many joints on both sides of the body	Affects a few joints often only on one side of the body	Affects only one joint
Rheumatoid arthritis	Common	Uncommon	Rare
Polymyalgia rheumatica	Common	Uncommon	Rare
Psoriatic arthritis	Common	Common	Uncommon
Lupus	Common	Common	Uncommon
Viral infections	Common	Common	Uncommon
Gout	Uncommon	Uncommon	Common
Bacterial infections	Rare	Uncommon	Common
Juvenile chronic arthritis	Uncommon	Common	Common
Reactive arthritis, ankylosing spondylitis	Uncommon	Common	Common
Osteoarthritis	Uncommon	Common	Common