Curvature scaling in the medial tibial condyle of large bodied hominoids

Abstract

The shape of joint articular surfaces can provide important information about the locomotor habits of animals. Understanding sources of shape variation in these surfaces is critical to correctly inferring the link between form and function. This study tests the hypothesis that increases in body size within a species result in flatter joint contours of the joint articular surface. Joint flattening is expected to regulate the magnitude and direction of transarticular stresses passing through the joint. Threedimensional laser scans of polyvinylsiloxane molds of the medial tibial condyle of gorillas (n = 40), common chimpanzees (n = 40), and modern humans (n = 40) were evaluated for differences in articular surface topography, with all measures of joint curvature examined in relation to femoral head superoinferior diameter (as a surrogate for body size). Analyses did not detect an allometric shape change in the curvature of the medial tibial condyle with increasing body size within any of the three taxa examined here. Medial tibial condyle curvature appears to be largely independent of body size as estimated by femoral head diameter. These results do not provide direct support for the hypothesis that joints become flatter in response to increased transarticular loading. © 2010 Wiley-Liss, Inc.