Have you ever seen an old gangster movie? When the tough guys are called in to deal with a problem, they often do one thing before tackling the problem. While facing the problem straight on, they intertwine their fingers and flex their hands outward, producing a loud popping sound.

You don't have to be a gangster in a movie to crack your knuckles, however. Just about everyone can do it from time to time. In fact, many people have all sorts of other joints that they can cause to crackle or pop. These might include their wrists, elbows, knees, ankles, or toes.

The cracking and popping sounds cause some people to cringe. When your joints make these sounds, is something wrong? Is it dangerous? Should it be avoided at all costs? Is there any way to prevent joints from making these sounds?

Don't worry! Popping and cracking joints are usually normal and nothing to worry about. Exactly why they make these sounds isn't well understood. However, scientists do have a few popular theories about what might make those sounds.

The most popular theory holds that the sounds are made by popping bubbles. Your joints are the meeting places of your bones, which are held in place and attached to muscles by connective tissues, ligaments, and tendons. To help lubricate the motion of all these separate parts in your joints, a thick liquid called synovial fluid surrounds your joints.

Popping your joints stretches the joints to a point where gases in the synovial fluid are pushed out. This process, called cavitation, forms bubbles in your joints. When you stretch them far enough, those bubbles pop and produce the cracking and popping sounds you hear.

It can take up to 30 minutes for gases to dissolve back into the synovial fluid. This explains why you usually have to wait a while before you're able to pop your knuckles again.

Other scientists believe there may be other things that can cause joint popping and cracking. For example, some believe that the movement of tendons and ligaments in and out of place might cause these sounds. Such sounds could also be caused by tendons moving over and around the ends of bones.

Finally, some scientists believe some of the cracking and popping sounds we hear in our joints could be the result of bones rubbing against each other or places where cartilage has been torn away. As parts of your joints move across these rough surfaces, pops and cracks might be produced.

All of these reasons sound like they could be potentially harmful, but scientists believe the joint popping and cracking isn't necessarily harmful. Specifically, studies have shown that there's no reason to believe that joint cracking leads to arthritis. Some believe that, over time, joint popping might lead to some minor soft tissue damage and a decrease in grip strength.

While some people might recommend that you not pop your joints, scientists note that popping joints often increases mobility in those joints immediately after popping. In addition, many people report that popping joints makes them feel more relaxed, because their joints are more flexible.

If you don't like the sound of cracking and popping joints, there's not a whole lot you can do about it. There aren't any medications to take or exercises to do that will necessarily prevent joint popping. Fortunately, there don't appear to be any major worries associated with joint popping. Doctors recommend only worrying about popping joints if you notice swelling or pain in conjunction with the popping.

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