Our joints can crack either by force of manipulation or normal movement. Some people’s joints crack when they walk up or down stairs, other people experience involuntary popping or cracking when they move their arms or stretch their back. Still other people manipulate the knuckles of their fingers to crack them willfully. Either way, there are a couple of explanations for what is happening when the body’s joints crack.

The joints of the body that often make a cracking or popping sound include the knuckles, the back and neck, the knees, ankles, and elbows. Sometimes the joints crack audibly and other times you may feel it without hearing a sound. What is happening when your joints crack could be the escaping of gases or simply the movement of tendons and ligaments within the joint.

A healthy joint is comprised of bone surrounded by smooth cartilage, which is protected by a capsule lined with synovial membranes that produces fluid. This fluid contains oxygen, nitrogen and carbon dioxide gasses. When joints crack, it could be the result of the joint capsule being rapidly stretched, which causes the formation and release of gas bubbles. The release of gas can cause the popping sound you feel and sometimes hear.

In an unhealthy joint, where cartilage is rough from deterioration, the sound of joints cracking may be produced simply from friction. Similarly, even in a healthy joint, friction can cause a person's joints to crack audibly. As the joints are compressed and expanded, the tendons can stretch out of place and then make a popping sound when they move back into their original place.

Some experts believe that willfully or forcefully causing joints to crack is unhealthy for the joints, but others believe it causes no lasting damage. Chiropractors often manipulate certain joints to the point of cracking and some people may get relief from aching finger or neck joints when their joints crack. However, if you experience pain when your joints crack or you have swelling of the joints, you should see a physician. They may recommend medication to relieve the pain and swelling and will check for damage to ligaments, tendons, or cartilage.