Start by holding your hand out and extending all of your fingers. Then slowly retract your thumb and hold it for a few seconds. Then do this with your index finger, middle finger, and so on. Try bending one finger inward while keeping it straight, as well as curled inward. You can reverse the direction or start from beginning again, but do this exercise repeatedly until the stiffness is reduced. This exercise is perfect for soreness or tension in the knuckles of the fingers.