Arthritis

July 28, 2011

Osteoarthritis and rheumatoid arthritis are the two most common types of generalized arthritis. Unfortunately, many think that the two terms are interchangeable but in fact, they are two very different diseases with different treatments. As treatments differ, it is vital that the correct diagnosis is made.

Osteoarthritis

Osteoarthritis is the most common form of arthritis. It is primarily a disease of the cartilage that cushions the joints, leading to progressive thinning of that cushion.

More than just “wear and tear” leads to osteoarthritis. Cartilage undergoes constant recycling of removing old cartilage and replacing it with new. With aging, the recycling process breaks down and osteoarthritis then begins to form.

The most common joints affected are the fingers, base of the thumb, hip, knee, spine, and the great toe (a bunion). Risk factors for developing osteoarthritis include: obesity, aging, and situations that put one at risk at certain joints. For example, occupations that involve repetitive knee bending, kneeling, squatting, or stair climbing are associated with an increased frequency of knee osteoarthritis.

The symptoms of osteoarthritis include pain, stiffness, and disability. Initially, the pain is only intermittent, typically associated with the use of the joint. With time, the pain can be more constant as the disease advances. With inactivity, the joint stiffens and can give the sensation of locking up when trying to move it again. Morning stiffness, after a full night of inactivity, usually lasts about 15-30 minutes. This is in contrast to rheumatoid arthritis where morning stiffness can last for hours. The mainstay of treatment for osteoarthritis is nonsteroidal anti-inflammatory drugs. Osteoarthritis is discussed in greater detail elsewhere.

Rheumatoid arthritis

Rheumatoid arthritis is a disease of a disordered immune system in which inflammatory cells attack the joints. Because of the aggressive joint inflammation, the pain is much more severe and disabling than that of osteoarthritis. Like most autoimmune diseases, rheumatoid arthritis is more common in women. Other risk factors for rheumatoid arthritis include age greater than 50, smoking, and relatives with rheumatoid arthritis. Because this is an immune system process, multiple joints are involved at the same time. The most common joints include the hands, wrists, knees, and feet, but any joint can be involved. The disease is usually symmetrical, in that the same joint is affected on both sides of the body. Because of the inflammation, morning stiffness can last for hours. Some patients develop rheumatoid nodules, which are bumps on their elbows. This is a sign of severe progressive rheumatoid arthritis.

Abnormal blood tests in rheumatoid arthritis patients include an elevated erythrocyte sedimentation rate (ESR) and C-reactive protein, which are both signs of inflammation. A positive rheumatoid factor can be suggestive of rheumatoid arthritis but it is not absolutely necessary to make the diagnosis. The presence of a positive rheumatoid factor means that a more aggressive form of rheumatoid arthritis is present which requires more aggressive therapy. Treatment of rheumatoid arthritis has two goals: to control pain and to stop the joint destruction. To control pain, nonsteroidal anti-inflammatory medications or sometimes prednisone can be used to control the inflammation. With decreased inflammation in the joints, the pain and stiffness will decrease. However, these medications cannot stop the abnormal immune system from attacking the joints: other medications are needed for this.

The mainstay of rheumatoid arthritis treatment has been methotrexate, which was originally a cancer drug. A low dose of methotrexate given once a week has been shown to significantly improve the symptoms of rheumatoid arthritis in most patients. Other immune system altering medications are used if methotrexate is ineffective.

Recently, technology has allowed medical researchers to create medications that specifically target immune molecules that are known to be the cause of the inflammatory process in the joint. One such molecule is tumor necrosis factor (TNF), which is a highly destructive molecule in rheumatoid arthritis, causing lots of inflammatory debris in the joints. One medication that targets TNF is etanercept (Enbrel), given by subcutaneous injection twice a week. Etanercept is a TNF receptor that binds up the circulating TNF and prevents it from affecting the joint. Imfliximab (Remicade) is an antibody to TNF that binds it so that the TNF cannot affect the joint. Imfliximab is given by intravenous infusion every 4-8 weeks. Both of these medications have revolutionized how rheumatoid arthritis is treated. These medications, as with all immune system altering medications, can increase the risk of infections. All patients who use these drugs should be closely monitored by their physicians.

We now approach rheumatoid arthritis much like we treat cancer, by attempting to put the disease into remission. Aggressive therapy can prevent future joint damage and avoid disability. Of course, aggressive therapy is associated with more potentially harmful side effects. Anyone who uses these medications must consider the potential risks and benefits of therapy.

SEE ALSO: Autoimmune disorders, Osteoarthritis

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