What is cartilage?
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. Cartilage can change shape because it contains more than 70 percent water, which can be redistributed with movement. For example, when force is applied to a knee, as in standing or walking, some water from cartilage enters the joint and coats the cartilage. When the force is no longer present, such as when you sit down, the water is reabsorbed and the cartilage regains its normal shape. Because cartilage does not contain nerves, you do not feel pain when these changes in shape occur.

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 wears away, tendons and ligaments stretch, causing pain. If the condition worsens, the bones could rub against each other.

What are the symptoms of osteoarthritis?

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

Who is affected by osteoarthritis?
Osteoarthritis affects almost 16 million men and women in the United States. The chance of developing osteoarthritis increases with age. Most people over age 60 have osteoarthritis to some degree, but its severity varies, and some people develop more severe symptoms than others.

What causes osteoarthritis?
There are several factors that increase the risk for developing osteoarthritis, including heredity, obesity, injury or overuse of certain joints.

People born with joint abnormalities are more likely to develop osteoarthritis. Being "double-jointed" also increases the tendency to develop osteoarthritis.

Some people have an inherited defect in one of the genes responsible for making collagen, a major component of cartilage. This causes defective cartilage, which leads to more rapid deterioration of joints.

Finally, people who are 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 increases the risk for osteoarthritis of the knee. Maintaining ideal weight or losing excess weight may help prevent osteoarthritis of the knee, or decrease the rate of progression once osteoarthritis is established.

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 extending into the joint margin are prone to develop osteoarthritis in that joint.

Overuse of certain joints increases the risk of developing osteoarthritis. For example, jobs requiring repeated knee bending increase the risk for osteoarthritis of the knee.

How is osteoarthritis diagnosed?
The diagnosis of osteoarthritis is based on a combination of the following factors:

• Your description of symptoms
• The location and pattern of pain
• Certain findings on physical examination

If fluid has accumulated in the joints, your doctor may remove some fluid from the joint (called joint aspiration) and examine it under a microscope to rule out other diseases.

While there is no blood test to diagnose osteoarthritis, some blood tests may be helpful to rule out other types of arthritis.

How is osteoarthritis treated?
Osteoarthritis is usually treated by medications, exercise, application of heat or cold to the painful joint, use of supportive devices such as crutches or canes, and weight control. Surgery may be helpful to relieve pain when other treatment options have not been effective.

The goals of treatment are to accomplish the following:

• Decrease joint pain and stiffness
• Improve joint mobility and stability
• Increase your ability to do daily activities

Medications
Medications may be prescribed to reduce pain caused by osteoarthritis. Pain-relieving medications include acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin, ibuprofen or naproxen. Some medications in the form of creams, rubs or sprays may be applied over the skin of affected areas to relieve pain.

Unfortunately, medications do not reverse or slow the progression of joint damage caused by osteoarthritis.

When you are prescribed any medication, it is important to meet with your physician regularly so he or she can detect the development of any side effects.

Exercise
Exercise is important to improve joint movement and to strengthen the muscles that surround the joints. Gentle exercises, such as swimming or walking on flat surfaces, are recommended because they are less stressful on your joints. Avoid activities that increase joint pain, such as jogging or high impact aerobics.

Heat or cold treatments
Heat or cold treatments may be recommended to provide temporary relief of pain and stiffness. These treatments may be given in the form of a hot shower or bath, or by applying heating pads or cold compresses.

Supportive devices
Supportive or assistive devices may be helpful to decrease pressure on the joints. Knee supports may be helpful for some people to stabilize the ligaments and tendons and decrease pain. Canes or crutches may be helpful to take pressure off certain joints.

Weight control
Staying at your recommended weight helps prevent osteoarthritis of the knees, reduces the stress on weight-bearing joints, and reduces pain in affected joints.

Surgery
When osteoarthritis pain is not controlled with these other methods, or when the pain prevents you from participating in your normal activities, surgery may be an option to restore function. Surgery involves replacing the damaged joint with an artificial one. Under the best of circumstances, though, surgery cannot return the joint to its normal state (artificial joints do not have all the motion of a normal joint). However, an artificial joint will very likely diminish pain.