Definition

Arthritis is a disease that involves inflammation of one or more joints. (Arthr refers to joints, and itis to inflammation.) See also joint pain.

Alternative Names
Joint inflammation

Causes, incidence, and risk factors

Joint inflammation is the body's reaction to various disease processes. These include mechanical injury to a joint (including fracture), the presence of an infection (usually caused by bacteria or viruses), an attack on the joints by the body itself (an autoimmune disease), or accumulated wear and tear on joints.

Often, the inflammation goes away after the injury has healed, the disease is treated, or the infection has been cleared by the immune system, sometimes with the help of antibiotics.

With some injuries and diseases, the inflammation does not go away or destruction results in long-term pain and deformity. This is considered arthritis. There are more than 100 kinds of arthritis with many different possible causes.

Osteoarthritis is the most common variety of arthritis in the United States. This arthritis often results from years of accumulated wear and tear on joints, and tends to occur in the elderly in hips, knees, and finger joints.

Gout, seen most often in males over 40 years old, is caused by the formation of crystals in the joints with subsequent inflammation. Gonorrhea is a bacterial infection that causes a so-called infectious arthritis. Autoimmune disorders, such as rheumatoid arthritis, lupus, and scleroderma, can cause arthritis as well. In these diseases, something goes wrong with the immune system, which then attacks healthy parts of the body (such as joints).

Arthritis can occur in males and females of all ages. About 37 million people in America have arthritis of some kind, which is almost 1 out of every 7 people. In people over 55 years of age, women are more likely to suffer from osteoarthritis. Other risk factors for osteoarthritis are obesity, a history of trauma, and various genetic and metabolic diseases.

Some of the diseases that cause arthritis include:

Osteoarthritis
Systemic lupus erythematosus (SLE)
Rheumatoid arthritis (in adults)
Juvenile rheumatoid arthritis (in children)
Gout
Scleroderma
Psoriasis (psoriatic arthritis)
Fungal infections such as blastomycosis
Ankylosing spondylitis
Reiter's syndrome/Reactive arthritis
Septic arthritis
Adult Still's disease
Tertiary Lyme disease (the late stage)
Tuberculosis (tuberculous arthritis)
Viral infections (viral arthritis)
Gonorrhea (gonococcal arthritis)
Other bacterial infections (non-gonococcal bacterial arthritis)

Symptoms

Patients with arthritis may suffer from the following symptoms:

Joint pain
Joint swelling
Early morning stiffness
Warmth around a joint
Redness of the skin around a joint
Reduced ability to move the joint
Unexplained weight loss, fever, or weakness that occurs with joint pain

Signs and tests

A physical examination may show that fluid is collecting around the joint. (This is called an effusion.) The joint may be tender (when it is gently pressed), and may exhibit warmth and redness, more typically in infectious arthritis and autoimmune arthritis. It may be painful or difficult to rotate the joints in some directions. (This is known as limited range-of-motion.)

In certain autoimmune forms of arthritis, the joints may become deformed, if the disease is not treated. Such joint deformities are the hallmarks of severe, untreated rheumatoid arthritis.

Tests vary depending on the suspected cause. They may include blood or urine tests, as well as joint X-rays. In septic arthritis, joint fluid is removed from the joint with a needle and examined for the presence of infection. See the specific types of arthritis.

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