Tuesday, February 10, 2009

Cracking Your Knuckles

You may have cracked your knuckles as a kid and had your mom yell, "Stop! That'll give you arthritis." Is this true or an old wives' tale?

Although cracking or popping knuckles is common, the research on it is not.

Let's start with two thoughts. What causes the popping sound, and what is arthritis anyway?

The cracking or popping sound is caused by release of gas, mainly carbon dioxide, out of solution in the synovial fluid of the joint.1,2,3 This is similar to the sound of a champagne cork releasing. The popping produces only a small increase in pressure in the joint, which has been estimated to be only 7% of the pressure needed to damage the cartilage of the joint.4 The gas takes out least 30 minutes to build back up. This is why you cannot immediately pop your knuckles again. However, other sounds may be re-occurring. For example, a snapping sound is usually a tendon or ligament sliding over a bone, and a crunching sound is usually damaged cartilage.

Arthritis is one of those words that is casually thrown around by both doctors and patients alike. Oftentimes, I'll have a patient tell me they have arthritis or a physician told them they have arthritis, and I'll ask what blood tests or x-rays have they had performed. Usually they'll reply, "none." Unfortunately, that does patients a disservice because several types of arthritis exist. The name arthritis means simply “joint inflammation”. The two main types of arthritis are rheumatoid arthritis (RA) and osteoarthritis (OA). Rheumatoid arthritis has been theorized to be an autoimmune disorder where the body attacks its own joints and causes joint inflammation including redness, swelling, and deformity. Often this has to be controlled by some type of medication and/or supplement. Osteoarthritis is wear and tear upon a joint which may result in joint space narrowing and bone spurs. Osteoarthritis is also caused degenerative joint disease or degenerative disc disease if found in the spine. A more proper name might be “osteoarthrosis” as it is seems to not have the inflammation involved with it as once thought. Psoriatic and gout are other examples of other types of arthritis one might hear.

Drs. Robert L. Swezey and Stuart E. Swezey in 1975 conducted a study of 28 nursing home residents who could recall whether or not they had cracked their knuckles earlier in life.5 After studying x-rays of the participants’ hands, the researchers concluded that there was no link between habitual knuckle cracking and arthritis.

In 1990, another study published in the Annals of Rheumatic Disease looked at a group of 300 habitual knuckle crackers.6 The researchers found that the participants who cracked their knuckles regularly were no more likely than those who did not to have arthritis.

Dr. Donald L. Unger released an article in 2004 where he reported to have spent fifty years cracking the knuckles of only his left hand twice daily.7 After analyzing the difference between his left and right hand, he found no noticeable differences and no arthritis had developed.

According to Sanjiv Naidu, Pennsylvania State University professor of orthopaedics, "Plain old knuckle-cracking should not cause any damage.8 It does not strain the ligaments or the tissues, or overextend them enough to cause arthritis," Naidu says. "It also should not cause joint weakness, on a long-term basis. Anatomically, physiologically, and mechanically, there's no reason it should cause harm."

Elaborates Naidu, "You literally have to disrupt the joint capsule through excessive force – like a ligament injury in a knee, or 'skier's thumb,' for example – to cause chronic, long-term damage.” The forces generated by knuckle-cracking are relatively small in comparison, Naidu said.

In my opinion, knuckle cracking is not necessarily a bad thing; however, taking the joint in the wrong direction so that it is misaligned can cause a host of problems. This is similar to spinal or extremity issues. “Popping” the joint is not going to hurt it if it is taken into a properly aligned position. However, if it ends up in the wrong position, acute pain might ensue or chronic wear and tear might occur over time. This is why having your body professionaly aligned is important.

Dr. V.

1. Brodeur R. The audible release associated with joint manipulation. J Manipulative Physiol Ther. 1995;18:155-164

2. Brodeur R. What makes the sound when we crack our knuckles? Sci Am. October 26, 2001.

3. Protapapas MG, Cymet TC. Joint cracking and popping: understanding noises that accompany articular release. J Am Osteopath Assoc. 2002;102:306.

4. Watson P, Hamilton A, Mollan R. Habitual joint cracking and radiological damage. Brit Med J. 1989; 299(6715):1566.

5. Swezey RL, Swezey SE. The consequences of habitual knuckle cracking. West J Med. 1975;122:377-379.

6. Castellanos J, Axelrod D. Effect of habitual knuckle cracking on hand function. Ann Rheum Dis. 1990;49:308-309.

7. Unger D. Does knuckle cracking lead to arthritis of the fingers? Arth & Rheum. 2004; 41:5:949-950.

8. Tibbett S. Probing Question: Does cracking knuckles cause permanent damage? Physorg.com. April 13, 2006.

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