What Causes Arthritis?

Posted: April 1, 2004

For many types of arthritic diseases, no cause is known. Researchers are looking at possible causes for many of these diseases.

With osteoarthritis, extreme stress on a joint may play a role in how this disease develops. Stress can be caused by weak cartilage (which runs in families) or from repeated injury to the joint.

Biological make-up and family history may play a role in gout, rheumatoid arthritis, lupus, ankylosing spondylitis, and some other arthritic diseases.

Researchers are also looking at why some people develop these diseases and others do not. Being overweight and aging appear to increase a person's chances of getting osteoarthritis. And, women are more likely than men to get lupus and rheumatoid arthritis.

What does arthritis do to a person's joints?
Osteoarthritis and rheumatoid arthritis – the two most common types of rheumatic diseases – affect a person's joints, causing discomfort and pain. The range of motion in a joint can lessen, making it harder for a person to perform daily activities. Sometimes the joint can lose all function and not be able to move.

In a normal joint (where two bones come together), the muscle, bursa (sacs of fluid that protect moving muscles, skin and tendons) and tendons (tissue that attaches muscle to bone) support the bone and help the joint to move. The synovial membrane releases a slippery fluid into the joint space. Cartilage covers the ends of the bone to absorb shocks and to keep the bones from rubbing together when the joint moves.

Joint with osteoarthritis
With osteoarthritis, cartilage breaks down and the bones rub together. The joint then loses shape and moves. The ends of the bone become thick, forming spurs (bony growths). Bits of cartilage or bone float in the joint space.

Joint with rheumatoid arthritis
With rheumatoid arthritis, the joint becomes inflamed and the synovial membrane becomes thicker. This causes the joint to swell, causing damage to bone and cartilage. Over time, the bone and cartilage gets destroyed. Space between the joint gets smaller, and the joint loses shape and moves.

Source: National Institute of Arthritis and Musculoskeletal and Skin Diseases

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