Body Mass Estimation from the Knee: Forensic Applications

Abstract

The estimation of living body mass from skeletal material can be a useful component of a forensic profile. Previously, forensic anthropologists have generally used body mass estimation equations derived either from the femoral head or from a combination of bi‐iliac breadth and stature. However, these equations were originally generated for use in archaeological or paleontological contexts, and therefore may not perform as well in modern sedentary populations. In particular, these equations may significantly underestimate body mass in overweight and obese individuals, which increasingly account for a greater percentage of living populations.Here, we present new body mass estimation equations derived from measurements of the knee in a modern sample of known body mass. This reference sample consisted of 110 living subjects who participated in the Baltimore Longitudinal Study of Aging. Mediolateral breadth measurements of the distal femur and proximal tibia were taken from anteroposterior radiographs of the knee, and used with recorded body weight to develop prediction equations. We compare the results from equations derived from the entire reference sample with equations derived from a sample that excludes obese individuals (BMI>30). We also compare equations derived from youngest recorded body mass with equations derived from older body mass recorded at the time of x‐ray.R square, % standard error of the estimate, and % prediction errors are minimized in equations that use youngest recorded body mass and exclude obese individuals. Although body mass for obese individuals is underestimated by all equations, it is best approximated by equations derived from the older recorded body mass that include obese individuals. This type of equation also provides very good estimates of body mass for overweight individuals (25<BMI<30). All equations overestimate body mass to some extent in normal weight individuals, but equations derived from young adult body mass excluding obese individuals perform best in this group. Comparison with other studies suggests that certain of these equations may better approximate body mass in obese and overweight individuals than previously used equations.Our results indicate that, due to increasing rates of obesity in modern societies, body mass estimation equations designed for paleontological use should be applied with caution in the forensic context. Equations derived from modern samples with a greater proportion of overweight and obese individuals will perform better in such cases.