Arthritis: A Joint Effort

Although disease incidence increases with age, "growing older is not enough to explain osteoarthritis," says Washington rheumatologist David Borenstein. "There are people who get the disease much earlier on." In fact, about 6 percent of U.S. adults age 30 and over have osteoarthritis of the knee and 3 percent have hip osteoarthritis. While about 70 percent of those over age 70 have X-ray evidence of the disease in at least one joint, only half of them ever develop symptoms.

People with osteoarthritis have a progressive loss of cartilage -- the shock-absorbing tissue in joints -- and changes in the underlying bone, including formation of bony outgrowths or "spurs." Cartilage loss shows up on X-rays, but the degree of loss has not been found to be a reliable indicator of disease severity or progression. These and other changes in and around the joint lead to chronic and sometimes crippling pain, enlarged joints and limitation of motion. In some people, only one or two joints are affected, while in others multiple joints are involved.

Besides age and genetics (studies show that predisposition to the disease is sometimes inherited), risk factors include being female or overweight, having a prior joint injury or knee malalignment (being bowlegged or knock-kneed) and participating in high-intensity, high-impact sports. Also increasing risk are jobs involving repetitious tasks or kneeling, squatting and heavy lifting and -- for knee osteoarthritis -- weakness of the quadriceps muscle.

Some findings about osteoarthritis have surprised researchers.

For example, while being overweight is thought to be a risk factor for osteoarthritis because extra weight taxes joints, a few studies have associated obesity with osteoarthritis of the hands, which are not weight-bearing, suggesting that metabolic factors may also be involved. Research has revealed that cartilage is not just "an innocent bystander" in osteoarthritis, says Hochberg. "Cartilage is a dynamic tissue, constantly undergoing degradation and repair." In osteoarthritis, the normal balance between these two processes is somehow disrupted.

Often, researchers believe, disease is caused by the interplay of two or more factors.

For Steven Newman, 45, of Potomac, increasingly painful knee osteoarthritis resulted, he's been told, from his congenital bowleggedness along with the stress he put on his joints during 13 years as a marathon runner.

Newman says he wishes he'd known the risks of his "no pain, no gain" attitude 17 years ago, when doctors first diagnosed knee osteoarthritis after surgery for torn cartilage. Instead, he says, "I kept on with my activities, ran another marathon and continued to destroy my knees."

When a second arthroscopic surgery on his knees revealed serious degeneration, he gave up running at age 37. Two years later, a car accident left him with osteoarthritis in his right shoulder, forcing him to give up his dental practice.

Now, as associate director of education for the Washington chapter of the Arthritis Foundation, Newman sticks to low-impact exercise like walking and biking and manages his pain mainly through mental and spiritual approaches, because years of liberally gulping ibuprofen for the pain have left his stomach sensitive to medications.