Dispelling Mom’s Myths

By
March 3, 2005

Mills College Weekly

So, I was sitting in the dark the other night, with just a wimpy little light shining feebly on the crossword I was trying to finish. In my frustration over being stumped, I started to crack my knuckles. The little pops were quite satisfying, albeit not as satisfying as a five letter word for clever would have been. So, my mind started to wander… If only my mother could see me now. There are dirty dishes in the sink. I didn’t wash the sheets this week. And here I am reading in dim light, cracking my knuckles, and, if I do say so myself, doing a beautiful job procrastinating. But will these transgressions lead to arthritis and glasses? Were those stories we heard growing up really true? Will we ruin our eyes if we read without enough light? Could we end up with swollen, sore joints if we crack our knuckles? I set out to answer these questions and what follows is what I uncovered.

Most people would agree that the sound of the person cracking his or her knuckles leaves something to be desired. But, aside from social graces, is there a compelling reason to forgo popping pleasure? Does cracking your knuckles really cause arthritis? After digging through the Journal of Manipulative & Physiological Therapeutics and the University of Chicago’s Ask a Scientist Web site, this one-woman jury is ready to rule. Arguably, there are very good reasons not to crack one’s knuckles, but the threat of arthritis isn’t one of them.

Our knuckles are joints, locations where bones meet and are held together by connective tissue and ligaments. There is a thick clear lubricating liquid at these meeting points called synovial fluid. When we move the finger bones back into or out of their normal position, the synovial fluid pressure changes. A combination of forcing the fluid from one part of the joint to another and the associated small bubbles result in the popping sound we hear. There is no medical evidence that this can lead to arthritis later in life.

But before you reach for a knuckle, there is another angle to consider. Cracking our knuckles leads to rapid stretching of the surrounding ligaments which could lead to chronic damage. A similar phenomenon affects major league baseball pitchers. The stretching associated with pitching a single game isn’t enough to cause damage, but over the years these pitchers are more prone to inflammatory knuckle pain than the rest of us. Certainly one can convincingly argue that the magnitude and intensity of the two stretches aren’t comparable, but then again, a dedicated knuckle cracker probably makes up for intensity with frequency.

What about reading without proper lighting? Will it ruin our eyes? According to HowStuffWorks.com and the Chicago Sun Times Health Question column, we don’t have to fear blindness. Reading with only mood lighting might give us a headache but it won’t cause any long term damage. The strain that one might feel during or after reading in dim light is caused by the mixed signals we give our eyes.

When we enter a dark area, our eyes begin adjusting. The rod and cone cells in the back of the eye produce more light sensitive chemicals and the iris muscles relax, allowing our pupils to dilate in order to collect as much light as possible. However, reading requires your iris and the muscles that control the shape of the lens in your eye to contract. The contraction facilitates focusing the small words on the retina, in the back of your eye. These mixed signals, to relax in order to collect more light and to contract for better reading focus, can lead to classical symptoms of eye strain. These include headaches, neck aches, sore eyeballs, blurred vision, and dry eyes. Our eyes dry up because we tend not to blink often enough under these conditions.

The good news is that all of these discomforts are temporary and will go away over time. If reading in dim light doesn’t bother you then don’t worry about it and read to your heart’s content. However, if you do find yourself experiencing discomfort, take a minute to focus on something across the room. This allows your eyes to rest and should minimize feelings of strain.


Dispelling Mom’s Myths was published on March 3, 2005 in Sports & Health

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