How: Lie down on your back. Place a rolled up towel, pillow, foam roller, or ball under your knee. Tighten your thigh and lift your heel up off of the bed to straighten your knee while keeping the back of your knee on the towel roll. Hold for 5 to 10 seconds if able. Do this exercise with each leg.
How often: Work up to 10 reps, 3 times a day.