Osteoarthritis of the Knee Linked to Overweight

Researchers reviewed 46 studies on risk factors for osteoarthritis of the knee and found that being overweight was associated with 28.8 percent of cases, and having a previous knee injury was associated with 5.1 percent of the cases. Vigorous exercise is not associated with knee osteoarthritis in middle-aged women (Osteoarthritis and Cartilage, January 2015;23(1):34–40).

What is Osteoarthritis? Osteoarthritis means that you have pain in a joint and your doctors don’t have the foggiest idea why. Your doctor orders many blood tests for the known causes of joint pain and all are normal. You do not have an immune disease such as rheumatoid arthritis, gout or any other known cause of joint pain. X rays may be completely normal or may show broken cartilage or narrowing of the joint (Ann Rheum Dis, Nov 1993; 52(11): 790–794).

Eighty percent of Americans have X-ray evidence of osteoarthritis by age 65, and sixty percent have significant pain. Osteoarthritis usually starts as gradually increasing pain in the knees, hips, hands or spine, at age 40 or older. Osteoarthritis more commonly affects the joints at the ends of the fingers and at the base of the thumb. Rheumatoid arthritis usually affects the middle joints of the fingers and the joints where the fingers attach to the hand. In osteoarthritis, joints on one side of the body often hurt more than the other side. In rheumatoid arthritis, the same joints usually are affected on both sides of the body. In both, the pain is usually worse in the morning when a person first gets up. In osteoarthritis, the pain usually lessens as the person keeps moving. In rheumatoid arthritis, the joints continue to hurt for more than an hour after a person starts moving about. Treatments include pain medications, physical therapy, weight control, and eventually total joint replacement.

Exercise Does Not Cause Osteoarthritis Osteoarthritis usually has no known cause, but it can follow trauma such as after a football injury of just falling. You are at increased risk for osteoarthritis if you are overweight or have: *joint cartilage fractures, *trauma to your knee that tears ligaments or damages cartilage, or *one leg longer than the other with excess force on the shorter leg.

Recent data shows that chronic exercise or joint loading does not increase risk for osteoarthritis. Life-time runners are at decreased risk for osteoarthritis. No good data show that people with regular joint loading, such as farmers or manual laborers, are at increased risk for osteoarthritis. However, if you have hip or knee pain, you are probably better off avoiding impact sports such as running or jumping and concentrate on sports with low impact such as pedaling a bicycle or swimming.

Excess Weight and Osteoarthritis The Framingham Study found that women who lost about 10 pounds had a 50 percent reduction in the risk of developing new symptomatic knee osteoarthritis. Many studies show that weight loss decreases hip and knee pain. Weight control is an important part of treatment for osteoarthritis. Several recent studies show that people who store fat in their bellies are at increased risk for osteoarthritis. Belly fat produces leptin and adiponectin which stimulate the body to produce cytokines, such as interleukin-6, which can damage cartilage.

Joint Replacement Try to delay replacing a knee or hip joint as long as possible. A general rule is to put off replacing a joint until it hurts so much that you cannot sleep at night. The artificial joint is held in place by a spike that is driven into the middle of a long bone. This markedly weakens that bone. If you fall with a replaced joint, you are at high risk for cracking the bone around the spike of the joint replacement. The broken bone around the spike may never heal so that you lose the ability to exercise that joint forever. If you have a joint replacement, you should restrict running and jumping and exercises that put you at high risk for falling. Choose exercises that use smooth motions such as elliptical machines, cycling or swimming.

Checked 1/14/16

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