The horizontal axis of the human body in the left and right directions is the coronal axis, which is one of the anatomical terms, and together with the vertical axis and the sagittal axis constitute the three basic axes of the human body. 1. Coronal axis: the human body in an anatomical position when standing in the left and right direction parallel to the ground and the sagittal plane perpendicular to each other, also known as the frontal axis, such as the humerus in the shoulder joint can be around the coronal axis of the flexion or extension movement. 2. Vertical axis: It is the axis that is perpendicular to the horizontal plane in the up and down direction, such as the femur in the hip joint can be rotated internally or externally around the vertical axis. 3. Sagittal axis: the axis that is perpendicular to the coronal plane in the anterior-posterior direction, e.g., the femur can move around the sagittal axis for adduction or abduction in the hip joint. These three basic axes are perpendicular to each other, and the joint movements of the human body generally rotate around these three basic axes.