With the increasing rate of obesity in the United States, the question has been posed: Does obesity lead to arthritis? To discuss this, I think that it is important to define what we mean by obesity and its affect on weightbearing joints. Obesity is typically defined as a body mass index greater then 30. The incidence of obesity in the United States has risen from 10% of males in 1960 to 28% of males in 2000 and for females from 16% in 1960 to 34% in the year 2000. During that timeframe, we have seen an increased rise in the incidence of arthritis. When we look at the incidence of arthritis in healthy individuals and compare the incidence of arthritis in the obese individual, there is nearly a 2 to 1 incidence of arthritis in the obese individual. In the morbidly obese individual with a body mass index of greater then 40, there is a four and a half times rate of arthritis involving the weightbearing joints.
The reason for this higher incidence of arthritis in obesity is due to the increased load placed across the surface of the joint. It is analogous to the half-ton pickup truck that is consistently overloaded with two tons of cargo. Eventually the shock absorbers and the tires wear out. In a similar fashion, our joints will wear out prematurely when they are chronically overloaded. For this reason, we counsel our patients to, within reason, increase their activity level and decrease their caloric intake to try to approach a more ideal body weight so as to preserve the function of their joints.
Joint replacement has been a very successful procedure in patients of all weight ranges. It has been documented that the incidence of complications and the longevity of joint replacement is different for the patient who is significantly obese.