Does Cracking Your Knuckles Cause Arthritis?

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Question: Does Cracking Your Knuckles Cause Arthritis?

Stop cracking your knuckles! That's a common plea from a parent trying to protect their children's hands, or from someone who's simply annoyed by the noise. Come to think about it, is cracking your knuckles just an irritating habit or is it actually harmful? Can cracking your knuckles cause arthritis?

Answer: Cracking your knuckles does not cause arthritis.

Understanding what physically occurs when you crack your knuckles will help you realize that the "knuckle cracking causes arthritis" theory is actually just a popular myth. That's good news if you like to crack your knuckles, but it's bad news to those of us who can't stand it when you do it. We'll have to come up with some other reason to get you to stop.

How the Knuckle Joint Works and Why You Can Crack It

A joint is formed where the ends of two bones come together. The ends of the two bones are covered by articular cartilage. The cartilage is surrounded by what is called the joint capsule. Inside the joint capsule, there is synovial fluid which serves as a lubricant for the joint and also as a source of nutrients for the cells that maintain the joint cartilage.

Synovial fluid contains dissolved gases -- oxygen, nitrogen, and carbon dioxide. When you crack your knuckles or when pressure is applied to a joint, the pressure inside the joint capsule expands but the expansion is limited by how much synovial fluid is contained in the joint.

Synovial fluid cannot expand unless pressure inside the joint capsule drops and the dissolved gases can escape out of the fluid. The cracking sound comes from the gases rapidly being released from the fluid.

Study Conclusions on Whether Knuckle Cracking Causes Arthritis

There have been a few studies over the years that considered whether or not cracking knuckles caused arthritis.

One study found that there was no increase of hand arthritis among knuckle crackers, however, knuckle cracking was related to hand swelling and lower grip strength.

Another study indicated that while knuckle cracking was not associated with arthritis, it was associated with damage to ligaments that surround the joint and dislocation of tendons. While cracking your knuckles is not linked to causing arthritis, there may be a connection to soft tissue injuries.

A study from 2011 looked at 215 people who had a hand x-ray within the past five years. It's interesting that 20% of them were habitual knuckle-crackers. The good news for those folks is that they were at no greater risk for hand osteoarthritis and it didn't matter for how long they had been knuckle-crackers or how often they did it each day.

Cracking Sounds You Don't Intend

People with arthritis of the hands or other conditions such as bursitis and tendinitis may feel snapping of the tendons and hear cracking sounds as the tendons can't glide easily over the swollen tissues.

These sounds and sensations may be why some think painless knuckle cracking might lead to arthritis. But they are not actually associated.

Sources:

Effect of habitual knuckle cracking on hand function. Annual of the Rheumatic Diseases. 1990 May;49(5):308-309.
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1004074

What makes the sound when we crack our knuckles? Scientific American. October 26, 2001.
http://www.sciam.com/article.cfm?id=what-makes-the-sound-when

Kevin deWeber, MD, FAAFP, Mariusz Olszewski, MD and Rebecca Ortolano, MD. Knuckle Cracking and Hand Osteoarthritis. J Am Board Fam Med March-April 2011 vol. 24 no. 2 169-174.

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