Why do human joints make cracking sounds?

People can move because various parts of the human body are composed of movable joints. The joints enable the human body to move freely. Therefore, people can perform basic actions such as running and jumping. However, some people find that their joints make noises when they exercise, and it has no effect on the body, at least not for a while. So, why do people's joints make noises?

When the joint first moves, the force of the tendon (such as tension, etc.) will instantly cause the joint to deform, which can increase to up to 7%. The deformation creates negative pressure in the joint cavity. Although this negative pressure is small, it is enough to cause the joint capsule to collapse (be sucked in), and to partially vaporize the nitrogen, oxygen, carbon dioxide and other gases dissolved in the synovial fluid into bubbles.

When the movement is about to be completed, the bubbles and synovial fluid are compressed, and there is a "pop" sound like popping champagne, which bounces the depressed joint capsule back to its original shape, and the gas dissolves back into the liquid. Also, because it takes time for the gas to dissolve back, the knuckle cracking sound can be repeated but not continuously.

Although the study pointed out that these noises are not enough to cause cartilage damage (less than 15% of the energy can damage cartilage), there is no need to worry about it. However, another 35-year follow-up of 350 people who cracked their knuckles for a long time found that these people generally had enlarged knuckles but weakened grip strength. From this it can be seen that those who enjoy doing this should exercise some restraint.

Of course, in addition to this mechanism, noises coming from the knee, ankle or back may also be caused by the taut tendons moving slightly and then bouncing back to their original position when the joints move; or there may be greater friction with the joint protrusions, causing the noises. If there is no redness, swelling, heat or pain, it should generally be no problem.

As for the sounds caused by joint degeneration and pathology, such as degenerative arthritis, cartilage erosion, and meniscus cartilage rupture of the knee joint, the sounds are usually accompanied by other symptoms and pathological changes. They are not the joint sounds described in this article and should not be confused. You should still seek medical treatment in the right way to avoid delays.

Why do human joints make cracking sounds? From the above introduction, we can know that there are many reasons for joint noises. It may be a problem with the physiological structure of the human joints themselves, or it may be a disease of the human body that affects the mobility of the joints and makes the joints prone to making noises. Therefore, people cannot ignore this issue.