Definition:
A crackling sensation or feeling created by hard tissue grinding together, or by air trapped under the skin. In the case of arthritis, inflamed joint surfaces may grind together, a sensation a person may feel. Broken bone fragments also can grind together to create crepitus. EMS workers will often try to move a suspected broken bone -- just a little bit -- to see if they feel crepitus.
To understand how crepitus feels, fill a plastic bag with gravel and squeeze it.
Another type of crepitus comes from little bubbles of air trapped in the spaces under the skin -- called subcutaneous emphysema. The little bubbles feel almost like weak bubble wrap.
