Secular Change In the Knee Joint and the Effects of Obesity
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In America, there have been well-documented trends of rising obesity in the past 30 years and a steady increase in stature during the 20th century. Proposed explanations for these increases in body weight and stature include changes in nutrition, over-nutrition, healthcare, sanitation, and socioeconomic status, as well as reduced incidence of infectious disease during early growth. Of interest to anthropologists is how excessive body weight affects the skeletal system. The purpose of this study is to: (1) determine if there is a secular change in the articular surfaces of the knee joint, (2) determine if there are differences between normal weight and obese individuals in the articular surfaces of the knee joint, and (3) examine if the secular change in body mass is a causal factor in the secular trends in the size and shape of the articular surfaces of the knee joint. Twenty-one measurements from the femur and tibia were collected and analyzed from 162 skeletons from the Robert J. Terry Collection, William M. Bass Donated Skeletal Collection, and the Texas State Donated Skeletal Collection. Body Mass Index was calculated for each individual using the CDC equation. The data were then subjected to statistical analyses to determine whether there has been secular change in the size and shape of the knee and to determine if obesity is a significant causal factor. The results of these analyses indicate a secular trend in several of the dimensions of the femur and tibia, and that there are differences between normal weight and obese individuals in some of these dimensions. However, the results are suggestive but inconclusive as to whether or not obesity is a factor in the secular trend. The results of this study support a growing body of literature that indicates obesity may have a significant effect on skeletal morphology.