Question:

I have been cracking my knuckles since 1995 and, today, they are very big and ugly. I have friends who have also cracked their knuckles for years, but their knuckles are not as big as mine. My fingers get very cramped and tight if I do not crack them. Do I need treatment?

Answer:

Although mom warned you this would happen, there appears to be no truth to the old wives' tale that cracking knuckles eventually leads to arthritis or enlarged knuckles. This popular misconception arises from the mistaken notion that the popping sound is caused by scraping of cartilage or bone that in some way damages joints.

What is really happening when you "crack" your knuckles is that you are actually pushing the joint either back into or out of its normal position. Joints in the fingers are composed of two bones, the ends of which are covered by cartilage and held together by a strong, fibrous capsule and ligaments. A lubricant found in the space between the bones is called synovial fluid, which contains gas (mostly carbon dioxide and some nitrogen).

When you crack your joints, the bones on either side of the joint space separate reducing pressure on the synovial fluid. This allows the gas to form bubbles that quickly expand and pop, causing the characteristic "popping" sound you hear. The sound is relatively loud because the synovial fluid is thick like molasses.

It takes about 15 to 30 minutes for the bones to return to their original position and another 10 minutes or so for the gas to be reabsorbed into the fluid. This explains why you cannot immediately crack your knuckles again. Fortunately, not everyone can crack their knuckles. Some people's joint bones are too far apart and others cannot relax enough to let the bones that comprise the joint separate. However, approximately 25 percent of Americans are habitual crackers.

Although little research has been done in this area, it is fairly safe to say that repeatedly pushing a joint beyond its normal physical range is not a good thing, and there is evidence that rapid, repeated stretching of the ligaments surrounding the joint can cause soft tissue damage to the joint capsule and a decrease in grip strength.

On the positive side, there is evidence of increased mobility in joints right after popping. When joints are manipulated, the muscles surrounding the joint are relaxed. This also may help explain why some people, including you, report an uncontrollable compulsion to crack their knuckles to relieve cramps and tightness.

If you feel you do not have a full range of motion in your finger joints or they are swollen and painful, it may be something more than the result of knuckle cracking for more than 20 years, such as osteoarthritis or other types of arthritis that involve the finger joints. Make an appointment with your physician to discuss the problem.