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What Causes Back Pain?

Why is the back such a pain? Dr. Rob gives tips to put the pain behind you.

By
Rob Lamberts, MD
Episode #030

What Causes Back Injury?

The most common back injury happens when you ask the back muscles to do more work than they should be doing. Back muscle injury happens either by a single incident of poor judgment, or by repeatedly asking them to do something they aren’t strong enough to do. The single incident goes something like this:

“Ah, look on the ground,” says the brain. “There’s a bag full of lead. If I pick it up I can show how strong I am and win back some of the macho points I lost trying to pass a football with my kid.”

“I can’t lift that!” the back muscles protest, “didn’t you listen in physics class about fulcrums, levers and torque?  We are barely strong enough to pick up a TV remote, let alone a bag of lead.”

“Physics, Schmysics! Do as I say!” commands the brain. “I am your master and you must do as I say.”

The muscles obey with the predicted outcome of injury, and possibly even muscle tear (depending on the stupidity of the brain). No macho points are gained.

Why Does a Back Injury Hurt?

I guess it goes without saying that back pain hurts, but what makes it hurt so much?  There are three sources of the pain: injury, spasm, and inflammation.  Injury happens when you bend over and pick up that bag of lead; muscles are stretched or torn, both of which cause immediate pain. 

The next thing that happens is muscle spasm.  When not working, muscles are usually relaxed.  When doing their work, muscles shorten, or “tighten up.”  When injured, muscles become tight, and prolonged tightness causes pain.

The last thing that happens is inflammation, which is the body’s way of fixing the injury.  White blood cells are sent to do the site of injury, releasing substances that speed repair.  Some of these substances, however, cause pain.  The process of inflammation is slow, not peaking until 48 to 72 hours after the injury.  That is why you hurt so much in the days after strenuous exercise. When old guys like me pretend we are young and fit, we injure our muscles.  Even if we don’t hurt immediately after exercise, the next few days are reminders of our non-young status.

What is a Pinched Nerve?

Sometimes the inflammation caused by the injury causes inflammation of the nerve root that is between two vertebrae.  When the nerve root is inflamed, it causes pain to go down the nerve that joins with the spinal cord at that level.  The nerve roots in the lower back (which is the most common place for injury) bundle together to form a large nerve called the sciatic nerve.  This nerve extends down the leg via the buttock and the back of the thigh. 

Nerve root inflammation associated with a muscle injury is experienced as an achey dull pain in the butt that goes down the back of the thigh.  That is called sciatica, and it’s more painful than it is dangerous when it happens along with significant pain in the back.  It’s more worrisome when the nerve root is injured by a herniated disc or by arthritis in the back, which present with sciatica without significant back pain.  I’ll cover all that in a future article.

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About the Author

Rob Lamberts, MD
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