It's a common misconception that cracking your knuckles can cause arthritis. Cracking the joints in your fingers can actually relieve tension and pressure located in the hands. The popping noise heard when cracking your joints, occurs due to nitrogen being pulled into the joint through negative pressure. Cracking and popping sounds can also be heard when tendons snap over body tissues due of minor adjustments in their gliding paths. As a general rule, painless cracking of the knuckles is not seen a dangerous.
Curl your left hand up into a closed fist with your thumb pointing away from the fingers; not tucked inside. Hold the left hand in front of your body and point it to your right. Your thumb should be pointing at your chest.
Flatten your right hand into a straight edge with your fingers close together. Connect the base of your palm with the bent knuckles of your left hand.
Push very gently with the palm of your right hand to exert some pressure onto the bent knuckles of your left. Curl the fingers of your right hand over the closed fist, if you need more leverage.
Crack your knuckles loudly by exerting more pressure over all four finger knuckles at the same time, until they crack. If done properly, you should hear the loud combined cracking of four joints and not just one.
Repeat with the right hand, but in the opposite directions.
Consult a doctor or medical professional, if you ever feel pain when cracking your knuckles. Pain may indicate underlying abnormalities in the structures of the joint; such as loose cartilage or damaged ligaments.
You can also gently pull on the ends of your fingers to stimulate a crack from the knuckles, although the sound is far quieter than pushing on them directly. Sufferers of arthritis, bursitis or tendinitis are likely to hear involuntary cracking sounds due to the snapping or irregular swollen tissues in the joints.
Do not force your joints to crack, if they are not making any noises -- doing so could lead to both temporary and permanent joint damage.