Table 4.

BVH-formatted definitions of joint motion.

Joint	Motion	Anthropology	Explanation
Hip	Flexion/Extension	Thigh lift forward for flexion (+), backward for (−)	Rotation in the sagittal plane around the frontal axis
	Axial rotation	Right thigh: Counterclockwise rotation from proximal to distal is internal rotation (+), and opposite is external rotation (−). The left side is opposite to the right side	Rotation in the horizontal plane around the vertical axis
	Lateral bend	Right thigh, Left thigh: both rotated medially for adduction (+) and opposite for abduction (−)	Rotation around the sagittal axis in the frontal plane
Knee	Flexion/Extension	The knee is bent backward for flexion (+), and opposite for extension (−)	Rotation in the sagittal plane around the frontal axis
	Axial rotation	Right thigh: counterclockwise rotation from the proximal end to the distal end is internal rotation (+), and opposite is external rotation (−). Left thigh: opposite to right thigh	Rotation in the horizontal plane around the vertical axis
	Lateral bend	Left/Right: knee-adduction (+), knee-abduction (−)	Rotation around the sagittal axis in the frontal plane
Ankle	Flexion/Extension	The back of the foot is pressed down and straightened for flexion (+), and opposite for extension (−)	Rotation in the sagittal plane around the frontal axis
	Axial rotation	Right foot: counterclockwise rotation from the near end to the far end for internal rotation (+), and opposite for external rotation (−); left foot: the opposite of the right foot	Rotation in the horizontal plane around the vertical axis
	Lateral bend	Inward turn: the direction of the outside of the foot along the ground (+); opposite for outward turn (−)	Rotation around the sagittal axis in the frontal plane