Osteoarthritis Health Center

The Basics of Osteoarthritis

Arthritis is a general term that means inflammation of the joints. Osteoarthritis, commonly known as wear and tear arthritis, is the most common type of arthritis. It is associated with a breakdown of cartilage in joints and can occur in almost any joint in the body. It commonly occurs in the weight-bearing joints of the hips, knees, and spine. It also affects the fingers, thumb, neck, and large toe. 

Osteoarthritis -- also called OA -- usually does not affect other joints unless previous injury , excessive stress or an underlying disorder of cartilage is involved.

Cartilage is a firm, rubbery material that covers the ends of bones in normal joints. Its main function is to reduce friction in the joints and serve as a "shock absorber." The shock-absorbing quality of normal cartilage comes from its ability to change shape when compressed (flattened or pressed together).

Osteoarthritis causes the cartilage in a joint to become stiff and lose its elasticity, making it more susceptible to damage. Over time, the cartilage may wear away in some areas, greatly decreasing its ability to act as a shock absorber. As the cartilage deteriorates, tendons and ligaments stretch, causing pain. If the condition worsens, the bones could rub against each other.

Who Gets Osteoarthritis?

Osteoarthritis affects an estimated 27 million Americans. The chance of developing the disease increases with age. Most people over age 60 have osteoarthritis to some degree, but its severity varies. Even people in their 20s and 30s can get osteoarthritis, although there is often an underlying reason, such as joint injury or repetitive joint stress from overuse. In people over age 50, more women than men have osteoarthritis.

What Are the Symptoms of Osteoarthritis?

Symptoms of osteoarthritis most often develop gradually and include:

• Joint aching and soreness, especially with movement
• Pain after overuse or after long periods of inactivity
• Stiffness after periods of rest
• Bony enlargements in the middle and end joints of the fingers (which may or may not be painful)
• Joint swelling

What Causes Osteoarthritis?

There are several factors that increase a person's chances of developing osteoarthritis. These include:

• Heredity. Some people have an inherited defect in one of the genes responsible for making cartilage. This causes defective cartilage, which leads to more rapid deterioration of joints. People born with joint abnormalities are more likely to develop osteoarthritis, and those born with an abnormality of the spine (such as scoliosis or curvature of the spine) are more likely to develop osteoarthritis of the spine. 
• Obesity. Obesity increases the risk for osteoarthritis of the knee, hip, and spine. Maintaining ideal weight or losing excess weight may help prevent osteoarthritis of these areas or decrease the rate of progression once osteoarthritis is established. 
• Injury. Injuries contribute to the development of osteoarthritis. For example, athletes who have knee-related injuries may be at higher risk of developing osteoarthritis of the knee. In addition, people who have had a severe back injury may be predisposed to develop osteoarthritis of the spine. People who have had a broken bone near a joint are prone to develop osteoarthritis in that joint. 
• Joint overuse. Overuse of certain joints increases the risk of developing osteoarthritis. For example, people in jobs requiring repeated bending of the knee are at increased risk for developing osteoarthritis of the knee.
• Other diseases. People with rheumatoid arthritis, the second most common type of arthritis, are more likely to develop osteoarthritis. In addition, certain rare conditions, such as iron overload or excess growth hormone, increase the chance of developing OA.