Crack Your Knuckles?

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crack knuckle2How many times have you heard that “cracking” your knuckles is bad for you? At least that’s what your mother always told you. And isn’t that popping sound that occurs during a chiropractic adjustment the same thing?

Well, the answers are no and yes. No, mom is usually right but not always (sorry mom) especially about the cracking knuckles.  And yes regarding that popping sound that occurs during an adjustment.

So, just what is that popping or cracking sound?  Synovial fluid in your joints contains oxygen, nitrogen and carbon dioxide gas. When a joint is rapidly pulled apart (think chiropractic adjustment or cracking your knuckles) the volume of the joint increases by 15-20%. This creates a partial vacuum (decrease in pressure) and the gas rapidly releases due to the pressure change. (Boyle’s Law, 1662). The ligaments of the joint that just got stretched out will slowly return back to a normal position and the gases will be compressed back into the synovial fluid. This takes about 20 to 30  minutes for smaller joints (hands) and longer in larger joints.

Experiment time: Crack your knuckles. Then immediately try again. No popping sound the second time. Now wait 20-30 minutes and try again. More popping.  I tell my patients that if you “pop”crack knuckle3 something and there’s no pain then you’re okay, but if there’s a pop with pain then you’ve got a problem and it’s time to come see me.

Sometimes when you get a routine chiropractic adjustment there’s no popping sound, why’s that?  Simple, the joint was not pulled apart far enough and/or fast enough. This is typically because the patient’s muscles may be too tight and won’t allow the joint to be pulled apart.  But then again, that doesn’t necessarily mean the adjustment didn’t take place because there are some powerfully effective chiropractic techniques that don’t elicit a “pop” or a “crack” in your joints or spine.

Okay, so is cracking your knuckles good or bad for you? Does cracking your knuckles really cause arthritis? Previous studies have NOT shown a link between knuckle cracking and hand osteoarthritis. One study even suggested that knuckle cracking helped prevent osteoarthritis*.

osteoarthritis[*Osteoarthritis (OA) is one of the most common forms of arthritis.  It’s a chronic condition in which the material that cushions the joints, called cartilage, breaks down. This causes the bones to rub against each other, causing stiffness, pain and loss of joint movement. The cause is not fully understood.  About 27 million people in America have osteoarthritis. Common risk factors include increasing age, obesity, previous joint injury, overuse of the joint, weak thigh muscles, and genetics.

Osteoarthritis symptoms usually develop gradually. At first, there may be soreness or stiffness that seems more like a nuisance than a medical concern.  Common symptoms include:

  • Sore or stiff joints – particularly the hips, knees, and lower back – after inactivity or overuse.
  • Stiffness after resting that goes away after movement.
  • Pain that is worse after activity or toward the end of the day.OA

OA may also affect the neck, small finger joints, the base of the thumb, ankle, and big toe.

The pain may be moderate and come and go, without affecting the ability to perform daily tasks.  Some people’s OA will never progress past this early stage. Others will have their OA get worse. The pain and stiffness of more severe osteoarthritis may make it difficult to walk, climb stairs, sleep, or perform other daily tasks.  If you have OA or suspect you do, you also need to see your chiropractor.]

crack knuckle4Knuckle cracking and hand osteoarthritis, Journal American Board of Family Medicine, April 2011: This study involved 215 people, of whom 135 had x-rays that showed they had osteoarthritis in their hands and 80 did not (healthy controls). The participants were aged from 50-89 years; they all had an x-ray of the right hand during the previous 5 years. The results: 20% of all the 215 participants cracked their knuckles regularly – 18.1% of those who cracked their knuckles regularly had hand osteoarthritis – 21.5% of those who did not crack their knuckles had hand osteoarthritis. None of them had evidence of neuromuscular, inflammatory or malignant diseases, factors associated with lower grip strength and hand osteoarthritis.

Ig Nobel Prize winner in Medicine in 2009, Dr. Donald Unger spent 60 years cracking the knuckles of his left hand but never his right. He reported no arthritis or other problems in either hand. Read about it: Here.

So there you have it, that cracking sound is not bad for your knuckles, but it sure can be annoying to listen to it when someone “cracks” their knuckles… especially at the dining table… or in public… or… anywhere.

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