Arthritis Home > Cracking Joints

The three reasons why your joints crack are escaping gases within the joints; the movement of joints, tendons, and ligaments; and rough surfaces within the joints (which can occur in people who have arthritis). The specific joints that are known to crack are the knuckles, knees, ankles, back, and neck. If the cracking causes pain in your joints, you should see your healthcare provider.

An Overview of Cracking Joints

For many, cracking joints brings back fond memories of childhood -- when it seemed like hours could be spent on this activity. But have you ever wondered why your joints crack? Or have you gotten older now and noticed that your joints have started to crack?
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." Joints crack because of three things:
  • Escaping gases
  • Movement of joints, tendons, and ligaments
  • Rough surfaces.
Escaping Gases
Scientists explain that synovial fluid present in your joints acts as a lubricant. This 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.
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Last reviewed by: Arthur Schoenstadt, MD
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