The functional morphology of weight bearing: limb joint surface area allometry in anthropoid primates
Journal of Zoology (1989) 218, 441-460
Sharon M. Swartz

Biomechanical scaling of long bone joint surface areas was investigated in 13 species of anthropoid primates. It was proposed that joint surface areas should scale with positive allometry with respect to body size in order to maintain relatively constant safety factors for joints in small and large animals and that modifications from the overall pattern of scaling may be expected in loading. Within anthropoids, the brachiating primates, white-handed gibbons (Hylobates lar) and black-handed spider monkeys (Ateles geoffroyi), were used to test this hypothesis. Total joint observed pattern of interspecific allomety supports the hypothesis that weight bearing is a major constraint on the design of joints. The positive interspecific allometry is reflected at the intraspecific level as well, with larger joints of larger species showing significant intraspecific despite their reduced compressive loading of the limb joints, even after controlling for joint mobility. These results suggest that, while evolutionary changes in locomotor behaviour that produce significant increases in loading of a joint may be accompanied by selection for increased joint surface areas, adoption of locomotor repertoires that reduce limb loading may have no selective effect on joint morphology, and joint design in these cases will reflect the biomechanics of the ancestral locomotor condition.