You might think that, because you routinely crack your knuckles and there’s nothing wrong with it, you don’t have to worry about popping in other joints, such as your jaw joint.
First of all, there are potential problems with cracking your knuckles (such as risk of acute injury, decreased hand strength, and swollen joints). And your jaw joint is a different type of joint from your knuckles, so the popping associated with TMJ has a very different cause, which is much more serious.
What Causes Cracking in Your Knuckles
Cracking your knuckles is kind of a mysterious event, and there are many things about it that aren’t fully understood. We know that the joints in your knuckles, known as diarthrodial joints, are made up of two bones with a piece of cartilage in between them, which is bound tightly in place by ligaments. The cartilage is bathed in fluid, and there are gases dissolved in the fluid.
When you physically manipulate your knuckles, you stretch them out, resulting in an increase in volume and a drop in pressure, which causes gases to come out of solution. We think that the cause of the sound–or the cause of part of the sound, since it’s composed of multiple parts–is this action of gases coming out of solution. This has been observed in a number of studies, including a recent detailed analysis by the University of California Davis, which used ultrasound to look at hundreds of people cracking their knuckles and repeatedly saw the same pattern to find that the sound of knuckle cracking is caused by the formation of the bubble, not the popping of it.
We know that knuckle cracking is probably not dangerous. Studies have shown that the activity is not linked to arthritis, though people who regularly crack their knuckles might have more joint swelling and a weaker hand strength than those who don’t crack their knuckles.
What Causes Cracking in Your Jaw
Jaw joint cracking, on the other hand, is caused by displacement of the cushioning cartilage. Your temporomandibular joint is a much more complicated joint, known as a condyloid joint, where the cushioning cartilage is not bound so tightly into place. It’s designed to have a little more freedom of movement to facilitate the complex motions of your jaw joint (your fingers just bend, while your jaw joint moves all over the place).
When the cartilage is displaced in the jaw joint, it might still cushion the two bones, but it’s unstable. At a certain point in its motion, it will slip back into place, which is what causes the click or pop. You’ll probably notice that your jaw tends to move irregularly along with the popping sound. You may also experience sharp jaw pain at this moment, though many people have more dull, aching muscular pain and don’t get sharp pains at this time.
Because jaw popping is linked to joint disc displacement, it can lead to jaw damage in a number of ways. First, this displacement stretches the ligament. Plus, it puts the ligament between the bones. This damages the ligament and may make it hard for the disc to slip back into place. If the disc can’t slip back into place, the jaw locks. In addition, when the disc isn’t in place, it does little or nothing to cushion the bones in the joint, which can lead to bone damage. As the bones grind, they can release tiny shards that irritate other tissues, leading to swelling, pain, and limited jaw movement.
Can You Have TMJ without Popping?
Yes. There are many reasons why you might not experience clicking or popping associated with TMJ. For some people, the movement of the cartilage doesn’t cause much noise or much disturbance of the motion of the jaw. In other words, you have have the popping, but it’s quieter and you may not notice it.
In other cases, you may have progressed beyond the point where your cartilage is slipping back into place. It may be so displaced that it’s no longer cushioning your jaw joint at all. (See our more detailed description of what joint problems mean.) In this case, you may hear a grinding sound of bones contacting, or you may hear nothing at all. Either way, the chances are good that your jaw joint is suffering serious problems at this point and if left untreated may require surgery to correct.