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Rheumatoid Arthritis of the Knee

Rheumatoid arthritis (RA) is a serious type of inflammatory arthritis that affects 1.3 million Americans. In 75% of cases, RA affects women. RA can affect people of any age, even very young children.

Unlike osteoarthritis (OA), the "wear-and-tear" arthritis, RA is a chronic autoimmune disease in which the immune system attacks the joints. RA usually occurs in a symmetrical pattern, affecting both hands, knees, ankles, feet, hips, elbows, and shoulders.

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RA causes severe joint swelling, joint pain, stiffness, and deformity. It also affects other tissues and organs such as the heart, skin, and lungs. RA can also cause fever, fatigue, weight loss, and flu-like symptoms.

Getting dressed, tying shoelaces, or walking to the car may be painful with knee arthritis. But with early and aggressive medical treatment, most cases of knee RA can be managed.

What Is Knee RA?

Rheumatoid arthritis of the knee causes the joints to become tender, warm, and swollen. Although knee osteoarthritis causes pain and stiffness, joint pain with knee RA can be more severe.

Normally, a small pouch covered with a thin tissue called synovium lies around the cartilage at the ends of the bones that connect to form a joint. Cartilage is a smooth material that allows for easy movement

The synovium secretes a liquid. This liquid helps keep joints lubricated. When joints are well lubricated, they move smoothly and painlessly. Inflammation of the synovium can lead to damage and permanent destruction of the joint by affecting both the cartilage and underlying bone

What Are the Signs and Symptoms of Knee RA?

With knee RA, you may feel the following:

  • Pain
  • Swelling, inflammation
  • Stiffness
  • Warmth around the knee joints
  • Fatigue


What Causes Knee RA?

The actual causes of RA are not understood. We know that RA occurs when the body's own immune system doesn't function properly.

RA may be linked to genetics. Environmental factors may also be involved by triggering events that lead to persistent over activity of the immune system.

How Is Knee RA Diagnosed?

Your doctor can diagnose knee RA. He or she will do a physical exam, talk with you about your personal and family medical history, and perform blood tests.

Blood tests for RA may be positive for the following:

  • Anemia (low red blood cell count)
  • Rheumatoid factor (RF), found in about 70% to 80% of those with RA
  • High erythrocyte sedimentation rate (sed rate), which indicates inflammation
  • Antibodies to cyclic citrullinated peptides (CCP)
  • High levels of C-reactive protein (CRP)

Your doctor may order an X-ray of the joints. An MRI may also be used to detect evidence of joint damage or destruction.

Your doctor may withdraw a sample of joint fluid (synovial fluid) to analyze. People with RA usually have joint fluid that's filled with inflammatory material.

WebMD Medical Reference

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