HOW: Laying on a table or elevated surface, make sure your knees are slightly hanging over the edge. Your knee cap should be just over the edge, comfortably. Let gravity pull your lower leg down and extend your knee. Hold that stretch as long as prescribed, usually until it reaches a point of discomfort.
FEEL: You should feel a stretch in the back of your knee. If performing after surgery or injury, it is common to be uncomfortable.
COMPENSATION: Keep the knee straight. Make sure your kneecap is off the edge of the table. Stay relaxed!