A PAIN IN THE BACK: I’m not a doctor — I’m an attorney who represents injury victims.  However, for many, many years, first as an attorney for an insurance company, now for victims of negligence, I’ve dealt with the anatomy of the back, and particularly with an ongoing problem — the bulging or herniated disk (what some people call a ‘pinched nerve’ in their back.)   Here’s a working explanation of what happens:

A CLOSER LOOK: Take a look at this anatomic diagram, which shows the structures of the spine and spinal column from the side, or profile view, as well as from a cut-through view from the top of the spine, looking down.

Here's a view of a spine with a herniated disk shown from the side and in a cutaway view for illustration.

UNDERSTANDING THE ANATOMY: The spine is made up of bony segments, or vertebrae, which house and shield the spinal column, a bundle of nerves which conducts sensation and motor signals to various parts of the body.  This particular section is the lumbar spine, or the low back (the ‘bottom’ portion of the spine).  Everyone (with certain very limited exceptions) has the same number of vertebrae, occurring in the same order.  Each vertebral is numbered so that doctors can keep track.

THE DISK’S ROLE: The disks are jelly-filled spongy shock absorbers between the vertebrae that cushion the spinal column as you move and are jarred.  (In the diagram, they’re the greyish, rounded objects between the vertebrae).  Among other purposes, they prevent the spine from crushing the ‘nerve roots’, which are the branches that come off the spinal column, out through the spine openings, and radiate out to various parts of the body.

HOW A DISK HERNIATES, OR ‘BULGES’: When a person suffers an impact or trauma, they can wrench or compress their back, causing the disk  (think shock absorber) to ‘squish’ outward or inward.  Since the outer surface of the disk is fibrous and tough, the disk can generally handle that and spring back.  However, sometimes the twisting or compression is so forceful that the disk’s outer fibers tear, and the inner ‘jelly’ escapes outward.  The disk will appear out of round and deformed, or ‘herniated’.  Depending on which physician you talk to, the terms ‘protruding disk’ and ‘herniating disk’ may be used alternately.

GETTING THE WHOLE PICTURE: The diagram shows a disc herniation at the space below the L5 vertebra.  You can see, in the right hand drawing, that the disk is protruding, or bulging outward.  In the cutaway view, (the middle picture on the right side) you can see that the disk has broken out of its round shape and is pushing forward.  Since the spine is closely ‘engineered’, there’s not a lot of room for this bulge, so that when the disk pushes out of its normal shape, or ‘herniates’, it can press on the nerve roots.  The results:  a distorted signal is sent back to the brain, resulting in the body experiencing pain, numbness, tingling or weakness in the area that the nerve root ‘feeds’ signals to.  (In the case of the L5 herniation shown here, the person experiencing the herniation would also tend to feel pain radiating down the back of their leg.  The side that experiences the herniation will likely experience the pain (a right sided herniation could produce pain or symptoms in the right leg; a left sided, the left leg).  With a lumbar herniation, this experience is often called ‘sciatica’, since the nerve that radiates out from this area is called the sciatic nerve.

This is an overly simplified explanation; there’s lots more that goes into diagnosing, assessing and treating spinal injury. The body’s natural degeneration over time, or spinal abnormalities which you’re born with but which don’t surface until you’re older, can also cause this phenomenon, for example, and many people walk around their whole lives with protruding disks that, because of their own particular anatomy, don’t trouble them at all.   But it’s a useful one, and I hope that it helps your understanding of what’s involved in a disk herniation, and how it can affect you.