The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)


An ill-named pair: Popliteal groove size does not indicate a high degree of popliteus muscle activity

BONNIE J. SUMNER, SUSAN G. LARSON and JACK T. STERN JR..

Department of Anatomical Sciences, Stony Brook University

March 27, 2015 11:15, Grand Ballroom A/B Add to calendar

A recent reconstruction of the locomotor pattern of Australopithecus (A.) sediba, suggested they utilized a gait with an unusual degree of hyperpronation, partly based on the presence of a deep popliteal groove on the distal femur thought to be caused by an enlarged popliteus muscle. The function of the popliteus muscle however, has only been explored in humans, and very little is known about the relationship between the size of the groove and activity (or size) of the muscle. We sought to explore the functional role of the popliteus in nonhuman primates, and clarify the relationship between the popliteus muscle and the popliteal groove through dissections of the popliteus muscle-tendon complex and measurement of popliteal groove dimensions. We collected electromyographic data on two humans, two chimpanzees, and one orangutan; linear and angular measurements of the popliteus groove on 15 catarrhine species; and performed soft tissue dissection on a chimpanzee, orangutan, mandrill, rhesus macaque, and a black and white colobus.. We addressed two questions: 1) when is the popliteal tendon within the groove, and 2) during what gaits is there high popliteus activity? The dissections revealed that the popliteal tendon is only within the groove during acute knee flexion. Popliteus muscle activity was highest during climbing for all subjects except one chimpanzee, but popliteus muscle activity did not coincide with acute knee flexion in any gait observed. Although there is predictable variation in the popliteal groove across catarrhines, there appears to be no functional link between the popliteus muscle and groove.

This study was funded by National Science Foundation grant BCS-0935321.