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How is osteoarthritis (OA) different from rheumatoid arthritis (RA)?

The immune system does not play a role in osteoarthritis (OA). Unlike rheumatoid arthritis (RA), a condition that causes some symptoms similar to OA, osteoarthritis is not an autoimmune disease.

Autoimmune diseases occur when the immune system mistakenly attacks healthy cells and tissues. Osteoarthritis is a condition caused by a wearing down of the cartilage that cushions the joints. This can be the result of age-related wear and tear, injury, repetitive movements or certain genetic conditions. Both RA and OA are painful and can interfere with work and day-to-day activities.

The immune system does play a role in osteoarthritis. It is triggered by tissue damage and causes a chemical called prostaglandins to be released resulting in pain, warmth and swelling. This is different from rheumatoid arthritis, which is caused by a misdirected immune response causing the body to attacks itself.

Dr. Suhail Kumar, MD
Rheumatologist

Rheumatoid arthritis is a systemic inflammatory disease primarily affecting the synovial joints causing significant pain, swelling, and significant morning stiffness. Although it primarily affects the joints, it can affect virtually any tissue or organ given that it is a systemic condition. Treatment consists of immunomodulators. In contrast, osteoarthritis results in degenerative changes from mechanical stress and trauma and is treated supportively.

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Unlike the more common osteoarthritis, which is mainly a disease of the cartilage in joints, rheumatoid arthritis (RA) occurs when the body's immune system attacks and damages the joints and, sometimes, other organs. RA often occurs in a symmetrical pattern, meaning that if one knee or hand is involved, the other one is too.

Arthritis is an umbrella name for more than 100 diseases, including lupus, gout, osteoarthritis (OA), and rheumatoid arthritis (RA), all of which affect a person's joints or connective tissues. But OA and RA are very different diseases, with distinct symptoms and treatments:

Osteoarthritis
When it starts: Later in life, usually after age 50    
Joints affected: Mostly hips, knees, feet, and spine; rarely affects hands           
Joint symptoms: Pain, swelling                                                         
Pain symmetry: No; pain often affects only one joint                               
Bone symptoms: Bony growths

Rheumatoid Arthritis
When it starts: Usually between age 30 and age 60, but can begin anytime
Joints affected: Tends to affect hands and feet first, but can affect any joints
Joint symptoms: Pain, stiffness, heat, redness, tenderness
Pain symmetry: Yes; usually occurs in joints on both sides of the body (e.g., both wrists or both ankles)
Bone symptoms: Erosion of bones in affected joints
Blood test results: Detect inflammation, anemia

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Dr. Mehmet Oz, MD
Cardiologist (Heart Specialist)

Let's begin with what osteoarthritis and rheumatoid arthritis have in common. Both cause joints to become painful and stiff. And both of these frustrating conditions can limit mobility, rob you of independence and lessen your quality of life.

However, osteoarthritis and rheumatoid arthritis are two very different conditions in other ways. Osteoarthritis (OA) isn't caused by immune system issues. Osteoarthritis seems to be brought on, at least in part, by wear and tear. Over time, protective tissue called cartilage in the joint withers away. That leaves bones scraping against bone, causing pain and other symptoms. The OA-related joint pain, swelling and inflammation doesn't spread to the rest of the body.

By contrast, rheumatoid arthritis occurs due to a glitch in the body's immune system. Normally, the immune system produces white blood cells to attack intruders such as bacteria and viruses. If you have rheumatoid arthritis, though, the immune system mistakenly sends white blood cells to invade and destroy tissue in the joints. In rheumatoid arthritis, the inflammation in the joints can spread to other parts of the body.

There are other differences between osteoarthritis and rheumatoid arthritis. The latter can affect body parts other than the joints, including the eyes, lungs, skin and blood vessels. Rheumatoid arthritis is also usually symmetrical; that is, if your right wrist is affected, your left wrist probably will be too.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.