924 THE JOURNAL OF BONE AND JOINT SURGERY The Popliteus Muscle

ABSTRACT: The popliteus muscle was studied dur-ing 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 exer-cises 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. The function of the popliteus muscle as an internal rotator of the tibia on the femur under static conditions is well known and was previously described by several au