You may be cracking your knuckle or heard somebody doing it, and wonder if it is good or bad for you. First of all, contrary to the belief, cracking your knuckle will not cause arthitis. No study found any link between cracking the knuckle and athritis. There is some study however, that showed in the long term, swelling of the joint and decrese strenght of the hand.
The popping noise you hear when you crack your knuckle, is from a negative pressure, within the joint. It is a process called, cavitation. The noise is created, when there is a bursting of bubble of gas, from the separation of the synovial fluid that coat the joint. It take approximately 20 min. for the gas to regenerate in the joint. That is why, if you try to recrack you knuckle right away, you will not hear any sound.
So, basically, cracking your knuckle, will not cause arthritis or any major damage to the joint, with the exception of, minor ligament damage and loosening, swelling of the joint, and possible decrease strenght of the hand in the long run.