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What Is Arthritis of the Knee?

What Causes Knee Problems?


Updated June 27, 2014

Question: What Is Arthritis of the Knee?

There are two general kinds of knee problems:

  • mechanical knee problems
  • inflammatory knee problems

Some knee problems result from injury, such as a direct blow or sudden movements that strain the knee beyond its normal range of movement. Other knee problems can be caused by arthritis.


Arthritis of the knee most often refers to osteoarthritis. In this disease, the cartilage in the joint gradually wears away.

In rheumatoid arthritis, which can also affect the knees, the joint becomes inflamed and cartilage may be destroyed. Arthritis not only affects joints, it can also affect supporting structures such as:

Osteoarthritis may be caused by excess stress on the joint from deformity, repeated injury, or excess weight. 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 experienced continuous irritation from an unrepaired torn meniscus or other injury. Rheumatoid arthritis often affects people at an earlier age than osteoarthritis.

Signs, Symptoms And Diagnosis

Someone who has arthritis of the knee may experience pain, swelling, and a decrease in knee motion. A common symptom is morning stiffness that lessens as the person moves around. Sometimes the joint locks or clicks when the knee is bent and straightened, but these signs may occur in other knee disorders as well. The doctor may confirm the diagnosis by performing a physical examination and examining x rays, which typically show a loss of joint space.

Blood tests may be helpful for diagnosing rheumatoid arthritis, but other tests may be needed too. Analyzing fluid from the knee joint may be helpful in diagnosing some types of arthritis. The doctor may use arthroscopy to directly see damage to cartilage, tendons, and ligaments and to confirm a diagnosis, but arthroscopy is usually done only if a repair procedure is to be performed.

Treatment Options

Most often osteoarthritis of the knee is treated with pain-reducing medicines, such as:

Exercise is essential to restore joint movement and strengthen the knee. Losing excess weight can also help people with osteoarthritis.

Rheumatoid arthritis in the knee may require physical therapy and more powerful medications. In people with arthritis in the knee, a seriously damaged joint may need to be replaced with an artificial one.


NIH Publication No. 01-4912. Questions and Answers About Knee Problems, National Institute of Arthritis and Musculoskeletal and Skin Diseases, May 2001

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