SIDE SLEEPING (SIDELING)
Position the pillow between the knees and ankles. In doing so, the knees, ankles, and hips will be parallel to one another. This prevents the joints from grinding together while decreasing strain to the ligaments and joints. This will also prevent the torso (thoracic spine) from torqueing in turn put less strain on the neck (cervical spine) and shoulders.
BACK SLEEPING (LAYING SUPINE)
Position the pillow under the knees. By raise the knees this will posteriorly rotate the hips toward the bed or laying surface in turn flattening the lumbar spine toward the laying surface. The pillow adds support to the lumbar spine ( Be sure your heels are touching the sleeping surface for proper use).