The Story of Sciatica

The number of people who come to my office thinking they have sciatica is many. Fortunately, the number who actually have it (in its true form), are few. Google, our friends, (or our friend’s friends), and our gross generalization of this condition often support the perpetuation of this common but inaccurate self-diagnosis. Sometimes people point generally to their back and report it’s their sciatica, others a leg, even others still, an arm. So what is it and where is it and what exactly is the story on this sciatica thing? To answer these questions, we first need to do a little anatomy to get ourselves orientated.

Spinal nerves exit and enter the spinal cord at each vertebral level as a thick “root”, and look sort of like the on and off ramps of a freeway. To visualize the rest of the nerve, we can think about it like a tree. If we take a tree, pull it out of the ground, roots and all, and lie it on its side, it’s similar to how some nerves look. Each tree is a bit different of course, but generally, we have the nerve roots closest to the spine (those on and off freeway ramps), then there’s a trunk portion, then there are branches after that. The branches are smaller than the trunk, come off at different places and are more wide-reaching. So we’ve got highways and trees and voila we have the spinal cord and nerves! The sciatic nerve (and its subsequent branches) is the longest and largest nerve in the body. This nerve is formed in the lower back and pelvis and runs down the back of the leg, all the way to the foot (so we’ve got one on each side). 

Now, the lumbar spine is the lower portion of the back; there are typically 5 lumbar vertebrae so we’ve got 5 corresponding lumbar spinal nerve levels, labeled as L1, L2 etc. Then we have the start of our tail, the sacrum, and (you’ve guessed it) we’ve got corresponding sacral nerves S1, S2 etc. The sciatic nerve is made by contributions from the nerve roots of L4-S3. So some cars from the exit ramps of L4, L5, S1, S2, and S3 can make their way onto this new road, called the sciatic nerve. This nerve then needs to make its way out of the pelvis so it must come through some of the deep gluteal muscles. The piriformis muscle is the landmark we use and depending on which anatomical variation you were born with, the sciatic nerve pops out of the pelvis either right above, right below, or right through the piriformis muscle. At this point, it is about the thickness of your pinky finger (large by nerve standards!). The sciatic nerve then continues down the back of the leg within the hamstring muscles. At about the back of the knee it then splits with one branch heading towards the outside of your shin and another continuing deep in the calf, both of these branch a couple more times before finally making it to the foot. So we’ve got the contributions from the nerve roots, coming together to form the sciatic nerve, which then branches and then branches again and so on. Got the rough idea of the map? Now we can finally get to what sciatica is. 

True “sciatica” is irritation of the sciatic nerve from something that affects the roots that contribute to the formation of the nerve (the spinal nerves L4-S3). This can be something like a disc herniation pushing on the nerve root or inflammation from a disc injury “dripping" on it, or a narrowing of the tunnel that the roots exit the protection of the spinal column in. This narrowing process, called stenosis (if significant enough), can be from arthritis of the small spinal joints that make up one side of the tunnel. Irritating a nerve can be extremely painful. Sometimes it can feel like a sharp stab or a lightening bolt down the path of the nerve. It can even cause a change in sensation (like burning, numbness or tingling) or a loss of sensation or strength. When it’s the nerve itself that’s irritated, we can usually point with our finger and trace the symptoms in a localized line that follows whatever nerve (or portion of nerve) is involved. In the case of sciatica, the pain can begin in the butt and travel down back of the leg and there may or may not be associated low back pain. You’ll notice this is the exact path of the nerve. It is not possible to have sciatica anywhere else in the body. For example, similar pain on the front of the leg would be coming from either a different nerve, or a different type of condition altogether. So that is the story on true sciatica, it’s irritation or pressure on the roots (one or more) that make up the sciatic nerve. It can be hard to treat because it’s coming from right up near the spinal cord in areas we can’t get at directly. We do have tools to help with it, but it’s a tough go and may require a range of treatments from manual or conservative therapy, medications or injections, to perhaps even surgery in some cases depending on the exact cause, extent of injury, and severity of symptoms.  

Pseudo sciatica, (aka false sciatica or piriformis syndrome) is when the pressure on the sciatic nerve happens not at the nerve roots, but rather as the sciatic nerve is trying to make its way out of the pelvis around (or through) the piriformis muscle. So these people may have very similar symptoms to someone with true sciatica, but the irritation is coming from slightly lower on the nerve. Usually from the piriformis muscle being too tight and compressing it somehow. Loosen the muscle up, and the nerve will be happier once it isn’t being squeezed. Good news is that although it can still be very painful and can sometimes also be stubborn to get rid of, we can access this muscle and work on it with a wide variety of therapies and stretches.

The other, very common cause of leg pain that seems to come from up in the back and is often mislabeled as sciatica is something called “referred pain”. Referred pain means that although we feel the pain in one area, it is actually being generated from a structure somewhere else. This type of pain is usually a bit harder for you to localize when describing it to a doctor. We can’t really trace it with a finger, we can just sort of use our whole hand to rub the general area that hurts. It usually isn’t as sharp and doesn’t have sensory changes, it’s more of a vague, dull ache. A couple culprits: the big SI joints (where the spine meets the pelvis) can often get stuck or inflamed and they, along with many of the muscles in the pelvis and ligaments of the lower back and pelvis can cause us to feel referred pain in the leg. Don’t worry, the pros go to school a long time and can help you sort it out. Depending on where it hurts and what happened, we can usually identify the tissue that your pain is actually coming from fairly quickly and addressing that will subsequently clear up the leg pain. 

Of course, this was just a rough guide to sciatica and leg pain for you. Some details are too detail-y for this discussion and there are complex pain patterns and variations - our bodies don’t always follow the “rules of the textbook” after all. So if you’re having pain in your back and/or leg an individualized exam and diagnosis should be made by a qualified professional. But at least now you know, contrary to your friend who has a sister who has a cousin who had sciatica - so you must too, and contrary to a quick google search, most leg pain is not actually sciatica. Nor is all low back pain (bad as it may be). And now that you know where the sciatic nerve is, you also know one thing for sure - that pain in your arm, it definitely ain’t sciatica ;)