The most common cause of popping joints is joint
friction. when two pieces of bone in a joint
, such as a ball and socket, rub against one another as you move. Sometimes it is also cartilage rubbing on bone. According to yoga instructor Paul Grilley, writing for Yoga Journal, joint friction is usually no cause for concern. You might not want to go out of your way to do it, but in the normal course of life it is harmless.