How Rheumatoid Arthritis Differs From Osteoarthritis(How Rheumatoid Arthritis Differs From Osteoarthritis )

Most people with arthritis have osteoarthritis, which commonly occurs with age.

But there's another type called rheumatoid arthritis (RA), a serious autoimmune disease. The two are often confused—which can be endlessly frustrating for those with RA.

"Everybody says that arthritis is one word," says Christopher Evans, D.Sc., Ph.D, the Maurice Mueller Professor of Orthopaedic Surgery at Harvard Medical School in Boston. "But the conditions are quite different."

Here are 13 ways to tell the two apart.

Age

While osteoarthritis is typically a disease of older people—often thought of as the result of years of wear-and-tear—RA can come on quickly at any age, even in children.

The average onset of RA is between 30 and 50 years old; osteoarthritis strikes most people later in life. (It's called juvenile RA when it occurs before age 16.)

"Unless you've been banged up on a sports field or in a car crash, it's very unusual to see someone with osteoarthritis at a young age," says Evans.

Numbers

Approximately 50 million people have arthritis in the United States, including half of those aged 65 or older.

About 27 million are cases of osteoarthritis and 1.3 million are RA.

Because of the big imbalance in numbers people often think all arthritis is osteoarthritis, and may say, "Oh, my grandmother has that" to someone with RA, or may not realize that yes, a child, teen, or young adult can indeed have arthritis.

Source of the pain

In osteoarthritis, cartilage in joints wears away with time leaving bone rubbing on bone. Ouch!

In RA, the immune system cells think they recognize an invader and target the synovium, the joint's lining.

Cell-signaling molecules such as tumor necrosis factor and interleukins pour into the blood stream, causing fever, swelling, and other symptoms not seen in osteoarthritis. (The inflammation caused by RA can lead to heart, lung, and eye damage.)

Medication

Osteoarthritis is treated with steroid injections (into the joint) and oral NSAID drugs like ibuprofen and naproxen (Aleve) to fight pain.

People with RA need these too, plus stronger oral steroids, like prednisone, which can cause bone thinning.

They also need drugs (some of the same ones used in chemotherapy for cancer patients, albeit at lower doses) that prevent joint destruction.

Known as disease-modifying antirheumatic drugs, or DMARDs, these meds are known for their effectivenes, and their risk of side effects or infections.

Joints

Both diseases affect the joints, but just where and how they cause trouble differs.

RA generally attacks smaller joints first, from the wrists to the toes, leaving them painfully red, warm and swollen, usually in matching sets, on both sides of the body.

In osteoarthritis, larger weight bearing joints such as hips and knees usually have the worst damage, and the problem joint may be on one side of the body but not the other.

"Rheumatoid arthritis can spread from one hand to the other and then throughout the body to as many as 30 different joints," Evans says. "Whereas osteoarthritis affects a very limited number of joints."