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How common are knee problems?
More than 4 million people in the United States seek medical care each year for a knee problem.
What causes knee problems?
Some knee problems result from "wear and tear," such as occurs in osteoarthritis. Other problems may result from injury, such as a blow to the knee or sudden movements that strain the knee beyond its normal range of movement.
How can people prevent knee problems?
Some knee problems, such as those resulting from an accident, can't be foreseen or prevented. However, a person can prevent many knee problems by:
Warming up before exercising or participating in sports. Warming up can be done by walking or riding a stationary bicycle. Stretching the muscles in the front of the thigh (quadriceps) and back of the thigh (hamstrings) reduces pressure on the tendons associated with the knee, and reduces pressure on the knee during activity. Strengthening the leg muscles with exercises like walking, by riding a stationary bike or by working out (under supervision) with weights. Avoiding sudden changes in the intensity of exercise. Instead, increase the force or duration of activity gradually. Wearing shoes that fit properly and are in good condition to help maintain balance and leg alignment when walking or running. Maintaining a healthy weight or losing excess weight to reduce stress on the knee. Obesity increases the risk of degenerative conditions such as osteoarthritis of the knee.
What kinds of doctors treat knee problems?
Significant injuries of the knee and severe knee disease are usually treated by an orthopedic surgeon. Patients who need non-surgical treatment for arthritis of the knee usually see their primary physician or a rheumatologist. Some doctors in physical medicine and rehabilitation (physiatrists) specialize in joint injury.
What is the function of the knee?
The knee joint works like a hinge to bend and straighten the lower leg. It permits a person to sit, stand and pivot.
What are the structures of the knee?
The knee joint is the place where three bones meet, namely:
The ends of the three bones in the knee are covered with cartilage, a tough, elastic material that functions as a shock absorber and helps the knee joint to move smoothly. The knee joint also contains tendons (tissue that connects muscles to bone) and ligaments (tissues that connect bones to other bones).
What diagnostic methods are used to evaluate the knee?
Doctors use several methods to diagnose knee problems. They may include:
Medical history (the patient describes symptoms and gives other information about what might be causing the pain). Physical exam of the knee. X-rays of the knee. Computed tomography (CT) scan, usually used for fractures, produces cross-sectional images of the knee, using x-rays and a large scanner. Magnetic resonance imaging (MRI) produces images in all three planes of the knee with the help of a large scanner, but without the use of x-rays. Arthroscopy - insertion of a fiberoptic tube into the knee through a small incision - to visualize the inside of the joint.
What is arthritis of the knee?
Arthritis of the knee is most often osteoarthritis, a degenerative disease in which joint cartilage gradually wears away.
Osteoarthritis may be caused by excess stress on the joint, such as from repeated injury, deformity or being overweight. It most often affects middle-aged and older people. A young person who develops osteoarthritis may have an inherited form of the disease or may have had continuous irritation from an injury that has not been repaired. In rheumatoid arthritis (which also can affect the knees), the joint becomes inflamed and cartilage may be destroyed.
Rheumatoid arthritis usually affects people at an earlier age than osteoarthritis and involves an abnormal immune attack on a person's own body cells. It is not certain what causes rheumatoid arthritis, although heredity is thought to be a factor. Rheumatoid arthritis can be associated with damage to other parts of the body.
What are the signs of knee arthritis?
A person with arthritis of the knee may have pain, swelling and decreased knee motion. A common symptom for people with osteoarthritis is morning stiffness that goes away after moving around. Those with rheumatoid arthritis may have persistent stiffness. Sometimes the knee joint locks or clicks when the knee is bent and straightened.
How is knee arthritis diagnosed?
A doctor may confirm a diagnosis of knee arthritis through a physical exam, blood test, x-rays, analysis of fluid from the knee joint, or other tests. The tests vary depending on the type of arthritis you have. The surgeon may also use arthroscopy to directly visualize damage to cartilage, tendons and ligaments and to confirm a diagnosis, but arthroscopy is usually done only if a repair procedure is to be done.
How is knee arthritis treated?
Most often, osteoarthritis of the knee is treated with pain-reducing medications, such as aspirin or acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen. For rheumatoid arthritis, stronger medications might be prescribed.
Exercises to restore joint movement and to strengthen the knee are also helpful, along with physical therapy in some cases for rheumatoid arthritis. Losing excess weight can help people with osteoarthritis by taking pressure off the knee.
A seriously damaged knee joint may need to be surgically replaced with an artificial one.
 A word about NSAIDs
NSAIDs (nonsteroidal anti-inflammatory drugs) are commonly taken to reduce pain and swelling, although they are not for everyone. Ibuprofen, naproxen and aspirin are all NSAIDs. Talk to your doctor about whether taking NSAIDs is safe for you, especially if you:
This article was reviewed and updated
June 2007.
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