The popliteus muscle was studied during both normal gait and a series of
planned exercises. Its activity during the walking cycle was shown to begin
shortly before heel-strike and to continue throughout three-quarters of the
stance phase. During the exercises the muscle was active during internal
rotation of the tibia on the femur, and during normal gait the phasic
activity of the popliteus coincided with internal rotation of the tibia on
the femur. It was concluded that the basic function of the popliteus is to
help to bring about and maintain internal rotation of the tibia on the
femur.