The simplest range-of-motion exercise is to draw the ABCs. Imagine your heel is the tip of a pencil. Draw capital letters from A to Z with your heel to improve your range of motion. As it becomes easier, increase the size of the letters.
This exercise improves range of motion. Stretching is the last form of exercise that stimulates the production of HA within your joint.
Another range of motion exercise that stretches muscles in your thighs calves.