One review in the Swiss Medical Journal found no evidence in any of the available studies that cracking your knuckles causes arthritis. A doctor even showed this by experimenting on himself. At the end of the experiment, the knuckles on his left hand were no different than those on his right hand, and neither hand showed signs or symptoms of arthritis.
Studies show that as many as 54 percent of people crack their knuckles. They do it for a lot of reasons, including:. The reason the joint makes a popping or cracking sound when pulled is still not completely understood.
For a long time, many people attributed the noise to nitrogen bubbles either forming or collapsing in the joint fluid. Others thought it came from movement of the ligaments around the knuckle. In a study , researchers watched knuckles while they were cracked using an MRI. They found that a cavity formed due to the negative pressure created when the joint was pulled apart quickly.
They determined that the sound was made by formation of the cavity. A study suggested that the sound was actually caused by the partial collapse of the cavity. A review of studies noted that it takes 20 minutes for the cavity to fully collapse so a new cavity could be formed.
If any of these things happen, something else is going on. The easiest joints to pop are the ones in your fingers the interphalangeal and the metacarpophalangeal joints.
As the joint capsule stretches, its expansion is limited by a number of factors. When small forces are applied to the joint, one factor that limits the motion is the volume of the joint.
That volume is set by the amount of synovial fluid contained in the joint. The synovial fluid cannot expand unless the pressure inside the capsule drops to a point at which the dissolved gases can escape the solution; when the gases come out of solution, they increase the volume and hence the mobility of the joint. The cracking or popping sound is thought to be caused by the gases rapidly coming out of solution, allowing the capsule to stretch a little further.
The stretching of the joint is soon thereafter limited by the length of the capsule. If you take an x-ray of the joint after cracking, you can see a gas bubble inside the joint. This gas increases the joint volume by 15 to 20 percent; it consists mostly about 80 percent of carbon dioxide. The joint cannot be cracked again until the gases have dissolved back into the synovial fluid, which explains why you cannot crack the same knuckle repeatedly.
But how can releasing such a small quantity of gas cause so much noise? There is no good answer for this question. Researchers have estimated the energy levels of the sound by using accelerometers to measure the vibrations caused during joint popping.
The amounts of energy involved are very small, on the order of 0. Studies have also shown that there are two sound peaks during knuckle cracking, but the causes of these peaks are unknown. It is likely that the first sound is related to the gas dissolving out of solution, whereas the second sound is caused by the capsule reaching its length limit. The nitrogen bubbles within the synovial fluid usually take 20 minutes to re-form in your joints before they can crack again.
Part of the appeal of knuckle cracking could be that minute lull, when gas bubbles are re-forming in the synovial fluid. Read: Dr. Does repeated knuckle cracking then lead to arthritis like the superstition says? Klapper, knuckle cracking itself does no harm to your fingers, neck, ankles, or other joints that pop and crack throughout the day—whether from normal day-to-day motions or compulsive habits like pressing our knuckles or twisting your neck until you hear that familiar crack.
However, if you experience discomfort while cracking, then there could be a pre-existing condition that is aggravated by twisting and pressing the joint. Skip to content. But the satisfaction is mostly in your head. Were your parents right about arthritis?
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