What Are The Risk Factors For Osteoarthritis?

The cause of OA is elusive in most cases. Nevertheless, physicians have noticed that certain groups have a higher rate of OA than others. You may find that you belong to one or more of these groups.

Age Greater Than 45 Years

Although OA risk increases with increasing age, not all people older than age 45 have degenerating cartilage in their knees and hips. The cartilage in patients with osteoarthritis looks different and has a different chemical composition when compared to “healthy” aged cartilage. Many experts now believe that OA is a disorder caused by a genetic susceptibility combined with injury to the joint. As we grow older, we accumulate more injuries to our joints, our ability to repair injured cartilage decreases, our weight tends to increase, and our chance of developing other forms of arthritis increases.

Female Sex

Women may have some unrecognized factor that predisposes them to accelerated cartilage wear, or perhaps women start out with thinner cartilage plates or have weaker supporting muscles or more lax supporting ligaments. Whatever the cause, women have a higher risk of developing OA. Before age 45, OA occurs more frequently in men; after age 55, it predominantly affects women. In the general population, the ratio of OA in men and women is 3:4.

Hereditary Conditions

Having certain hereditary conditions can predispose you to OA. These conditions include congenital hip dislocation, defective cartilage, and malformed joints. Conditions such as being knock-kneed or being bowlegged also increase the chances for wear and tear in the joint. Additionally, people who have close relatives with OA are at a higher risk for developing it themselves. This increased risk may be the result of a defect in the gene responsible for the formation of collagen, which is an important component of cartilage.

Collagen

The major protein of connective tissue, cartilage, and bone.

Ethnicity

The rate of OA is not the same for all ethnic groups. Indeed, both the rate of OA and the distribution of joints affected vary considerably across ethnic groups. In the United States, Caucasian Americans and African Americans have higher rates of OA than Hispanic Americans or members of other ethnic groups. The rate of knee OA in African Americans and Caucasian Americans is about the same, but the rate of OA of the hips is 33% higher in African Americans than in Caucasian Americans. In contrast, Asian Americans have a lower risk of hip OA than Caucasian Americans. Ethnic differences in the rates of OA may be explained by genetic factors that determine the height, weight, joint angles, amount of force, and other structural factors in the joints. Other genes that regulate the chemistry of joint cartilage may also account for these ethnic differences.

History of Joint Injuries

Joint injuries caused by physical activity or sports increases your risk of OA. Football players and ballet dancers, for example, are at higher risk for OA because of the stress that these activities place on their knees and hips. Swimmers and baseball players can suffer from OA of the shoulder or elbow for similar reasons.

Obesity

Obesity, which is defined as being 20% over one's healthy weight, is a known risk factor for OA. Being obese dramatically increases the stress on weight-bearing joints and accelerates degeneration once OA has started. Obese people commonly develop OA of the hips and knees, but they also have a higher risk of developing OA of the fingers. Some scientists have suggested that excess fat tissue causes increased cartilage inflammation even in non-weight-bearing joints.

Other Arthritis

People who have another disease that affects the joints are at a higher risk for developing OA. Diseases such as rheumatoid arthritis, hemochromatosis, gout, and pseudogout, for example, can change the normal structure and function of cartilage and lead to early degeneration.

Education

As unlikely as it sounds, your level of education is associated with your risk of OA. Medical studies have found that the incidence of OA is highest in people with lower educational levels. One study, completed in 2000, demonstrated that college graduates had half the rate of OA as compared to those people who didn't graduate from high school. It is unlikely that reading and studying somehow make your joints healthier. Instead, college graduates may merely represent a different population of people from those without a high school diploma. College graduates, as a group, may have different ethnic backgrounds, have a lower ratio of women to men, and be less likely to be engaged in occupations that require physical labor as compared to people who didn't graduate from high school.