Eat Your Spinach

Mom always told us to eat our spinach. It will make us strong. We believed. We ate. And we walked away from the dinner table to gather our capes and plastic swords to battle the bad guys down the hallway. Good thing only my sisters lived at the end of the hallway because I ate a lot of spinach. Dad always said I would grow hair on my chest if I ate sardines.

"Now these will put hair on your chest," he said. I can still remember his smile as he bit the heads off at the dinner table, making my sisters run back down to the end of their hallways where I would later confront them with my spinach-bolstered bravery...er...knavery--with no hair on my chest.

Okay, so this blog entry has a point. Spinach. I love you Mom, but maybe moms have been known to be wrong about a few things--propagating healthy rumors that are nothing more substantial than rumor.

Knuckle cracking. Known as "KC" in the literature. Has Mom ever told you it will give you arthritis? Well I finally came across an elegant (elegant in every sense of the word) study by a physician who found KC does not cause arthritis.

For fifty years he diligently knuckle cracked his left hand at least twice a day. Yes, 50. He refrained from cracking his right hand during this time, and any crack on the right was unintentional. How he did this for fifty years amazes me because I always feel unbalanced if I crack only one side of any part of my body. But he cracked unilaterally, and diligently. And then he imaged his hands and compared the two, finding no evidence of arthritis in either hand, in fact, both hands showed similar joint space findings.

You can check out his paper here:

1. Unger DL

. Does knuckle cracking lead to arthritis of the fingers? Arthritis Rheum 1998;41:949–50.

I finally learned the physiology of knuckle cracking this week. We have ligaments over our joints to provide stability. In between the ligaments is a synovial film, or fluid layer. When we apply pressure to the joint we separate the ligament layers and create a negative pressure within the synovial film layer where air quickly rushes in. The air rushing in is the "pop" we hear. And we can't pop it again right away because it's already full of air. The air must be reabsorbed out of the synovial film space before we can pop it again.

So thanks to Unger at least I can stop worrying about arthritis in my neck, back, knees, fingers, and toes, because the best thing at the end of the day is a little KC!