What causes the noise when you crack your joint

Escaping gases, movement and rough surfaces.

Your joints can make a variety of sounds: popping, cracking, grinding, and snapping. The
joints that "crack" are the knuckles, knees, ankles, back, and neck. There are different
reasons why these joints "sound off".

•  Escaping gases:Scientists explain that synovial fluid present in your joints acts
as a lubricant. The fluid contains the gases oxygen, nitrogen, and carbon dioxide.
When you pop or crack a joint, you stretch the joint capsule. Gas is rapidly
released, which forms bubbles. In order to crack the same knuckle again, you
have to wait until the gases return to the synovial fluid
.
•  Movement of joints, tendons and ligaments: When a joint moves, the tendon’s
position changes and moves slightly out of place. You may hear a snapping sound
as the tendon returns to its original position. In addition, your ligaments may
tighten as you move your joints. This commonly occurs in your knee or ankle, and
can make a cracking sound.

•  Rough surfaces:Arthritic joints make sounds caused by the loss of smooth
cartilage and the roughness of the joint surface.
Is joint cracking harmful?If you are feeling pain when your joints pop, than you should
seek a health care professional. In terms of knuckle cracking, somestudies show that
knuckle cracking does not cause serious harm. Other studies show that repetitive knuckle
cracking can do some damage to the soft tissue of the joint. It may also lead to a weak
grip and a swelling hand.