Osteoarthritis

Osteoarthritis (OA) is the most common type of arthritis. It can affect any joint in the body, but the hips, knees, hands, and spine are frequently involved. Among adults over 60 years of age, 17 percent of men and 30 percent of women suffer from the debilitating effects of the disease. It results from degeneration of the joint cartilage and changes in the surrounding bones, muscles, and soft tissue. Obesity and osteoarthritis coexist in a large segment of the population. Obesity plays an important role in the etiology and progress of osteoarthritis because of the impact on weight-bearing joints. Management of obesity significantly improves symptoms of osteoarthritis and is a key element in the treatment plan.

Types of Osteoarthritis

Primary osteoarthritis is the result of age-related degeneration in the joint. This type is seen in the elderly and involves multiple joints. What makes the joint cartilage susceptible to faster breakdown is the progressive loss of water content along with changes in the protein composition. Secondary OA is seen in younger individuals who have previously had a trauma or surgery. This type may affect just one or two joints. Younger individuals with congenital or developmental disorders of the bone or joint can develop symptoms of OA before the age of 40.

Risk Factors

Several factors predispose to osteoarthritis. Genetic factors have been noted to be important in hip osteoarthritis and hand joint arthritis in women. Being obese or overweight is strongly related to the risk of having knee arthritis. Some studies have also linked obesity to hip and hand arthritis, although the association is not as strong. Having a higher body mass index (BMI greater than 25) before the age of 30 increases one's chance of developing arthritis of the knee by age 60. In fact, the risk is threefold higher among overweight and obese young men and nine times among women as compared to their normal weight peers. Other risk factors for developing OA are previous joint surgery, injury to a joint, diabetes, and excessive strain as a result of work.

How Obesity Causes Osteoarthritis

Even though OA is often thought of as “wear and tear” arthritis, there is a complex interaction between mechanical and chemical factors within the joint. The joint cartilage in overweight individuals is subjected to greater mechanical stress and can undergo faster breakdown. This is especially true in the weight-bearing joints with a more marked effect on the knees than the hips.

Obese individuals have a higher incidence of OA in joints that are nonweight-bearing as well, for example, the hands. This has led to theories of chemical substances playing a role. These chemicals called cytokines are released from the fat cells and can alter [Page 565]the synthesis and breakdown of the proteins that support the cartilage. High levels of insulin as seen in individuals with diabetes may also be important in the evolution of OA.

Symptoms of Osteoarthritis

The most common symptom of OA is pain. It is worse with activity and relieved with rest. Pain can lead to significant impairment in the ability to carry out daily activities. With long-standing disease, however, pain may be absent, although there may be significant deformity. Slight stiffness is another common complaint, often experienced in the morning or after a prolonged period of rest to the joint.

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