The Medical Minute: Bone and joint disease not always arthritis

October 16, 2006

By John Messmer
Penn State Family & Community Medicine
Penn State Milton S. Hershey Medical Center
Penn State College of Medicine

Who has not had a painful joint? Perhaps it was a sore shoulder from lifting or a knee after a long walk. This is the annual National Action Week of the Bone and Joint Decade -- a week to focus attention on prevention and treatment of diseases of the bones and joints. There are many rare and uncommon forms of bone and joint disease but joint pain is something all of us will likely experience at some time.

In the United States, arthritis has been diagnosed in one in five Americans. Most people with arthritis are older. According to the Centers for Disease Control, more than half of people over 65 have had arthritis diagnosed, whereas fewer than 8 percent of those under 44 have the diagnosis. As one might expect, being overweight increases one's chance of having arthritis. What most people do not realize, however, is getting less exercise actually increases the risk of arthritis. That's right -- inactive people are more likely to have arthritis. Perhaps it is because people try to rest a painful joint that they think exercise causes arthritis, but that is a misunderstanding.

Osteoarthritis or OA is probably the most common type of arthritis. In osteoarthritis, the cartilage surface of the joint deteriorates and the inflammation that results causes pain and probably makes it progress. Joint trauma predisposes to it. Whether from being overweight or sustaining an injury or the force of repetitive impact on the joint, over time the cartilage fails, leading to arthritis. It's extreme trauma that is the problem, not just routine exercise which appears to reduce the risk. Running, even marathon running if done properly, would not be a common cause. Getting tackled in football or falling onto a knee might. It takes years to develop in most cases, which is why it is more common in older people. In addition to exercise, good nutrition probably lowers the risk.

Rheumatoid arthritis (RA) is different. In this disease, the immune system incorrectly attacks joints and destroys them. In some cases, an infection such as Lyme disease triggers it. In many cases, the trigger has yet to be identified. Whereas in osteoarthritis, the immune system is responding normally to joint surface injury, in rheumatoid arthritis the immune system action is abnormal and inappropriate. RA and a group of similar diseases are called "autoimmune diseases" because a person with the disease is attacked by his or her own immune system. Fortunately, great progress has been made in treatments that shut down the immune attack and preserve the joints.

Not every joint pain is arthritis. Inflammation of the joint surfaces is arthritis, but the soft tissue structures around the joint -- the tendons, muscles, ligaments and bursae (the fluid filled sacs at some joints that act as cushions) -- also can be painful and act like arthritis. It can be difficult for nonphysicians to tell the difference. Overuse is a common cause of these soft tissue inflammatory processes collectively called "enesthopathies." The rotator cuff of the shoulder, a group of four muscles that move the shoulder around, is a common source of tendonitis. The hips and knees are often the sites of bursitis. Unlike arthritis, the joints are not damaged by these problems, although severe tendonitis could lead to a torn tendon, particularly in the shoulder.

Fibromyalgia, formerly called "rheumatism" is another problem that acts like arthritis. Poor sleep and inadequate resting of the muscles may contribute to this. See http://live.psu.edu/story/16622 for more details on fibromyalgia.

Back pain can be from arthritis, but most often it results from lifting improperly or from wear and tear on the discs between vertebrae. Peoples' spines were designed to flex, but every time they move from being vertical, they exert extreme pressure on the discs that allow this movement. They can fail just like a rubber tube can fail after repeated bending. People can reduce the risk of disc injury by keeping their spines straight in the vertical position when lifting and by supporting their upper torsos when they do bend.

Remember -- good nutrition and regular exercise are as important in joint health as they are in the health of just about every other part of our bodies. Even if people do develop arthritis, exercise remains an important part of maintaining joint function.

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Last Updated March 19, 2009