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If Only I Knew...
About Sciatica

marie catherine bruno owner of the sole mate

By Marie-Catherine Bruno, BScPT, Cped(C).

The back is a very complicated area. It is complicated not only because a ton of muscles, nerves and blood vessels cross the area, but also because over 30 bones (meaning over 90 joints and more than 100 ligaments) lie in this area. No wonder why back problems are often misdiagnosed, last forever and are feared by the less experienced health professional.

Like any other joint, the typical back joint is composed of 2 bones (vertebrae), with 2 articulations on each side (the facet joints), and a big central articulation with the disc (a cushion full of gel) that lies in between every vertebra. Each vertebra is pierced in the front (spinal canal or vertebral foramen) to let the spinal cord run through it. All together they move, but they are also held in place by layers of ligament. The smaller joints (facet joints) are filled with a liquid (synovial fluid) and covered by a capsule. So like any other joint (the shoulder let’s say), they can become stiff and stop moving.

Now as if the vertebral joint is not already complicated enough, here come the nerves. On each side of the joint and on every joint of the spine, a nerve root derived from the spinal cord comes out of a space created between the two superposed vertebrae called the intervertebral foramen. This nerve root travels through muscles and can go as far as the tip of the fingers or the tip of the toes. They carry information in a bidirectional way (coming out and going into the spinal cord) regarding sensation, pain, and movement.

What can go wrong?

Because of the complicated anatomy, you can see why a lot of things can possibly go wrong. Unlike a fairly simple joint (the knee for an example), the diagnosis becomes very tricky. And we are all aware that unless we know exactly what is going wrong in the body, it is very difficult to fix it (just like a car, it will take a lot of time and a lot of money!). So anyway, what can possibly go wrong and cause so much pain? A lot! And for that particular reason, we will focus on the low back for now, which seems to affect a lot of runners and orienteers.

The Joints

Have you ever had a car or a bike accident? Or a bad enough fall that you could barely walk for a few days after it? Do you work in a very static position? Do you feel like your posture is not very good? A positive answer to any of these questions may mean that you are living with a joint problem!

The joints in your spine are like any other joint: they take a hit, they protect themselves and stop moving. Why then don’t you get as stiff as if you would have sprained your ankle? Well, simply because there are so many other joints in your spine, that the healthy ones will take the load and compensate for the few joints that are stiff. The result: a few days later you will feel like a new one, and will forget about what happened. Unfortunately, if those injured joints are not rehabilitated, they will remain stiff and cause some problems later.  What do you do when you have a stiff neck and cannot look into your car mirror? You simply turn your shoulders along so that you can see, don’t you? Well, that is called a compensation. When a whole segment is seized up, like your whole neck, you compensate using another body part, and you are normally fully aware of it. But when we are talking of a small joint tucked in within 32 others, you may not notice it. In the long run, the joints above and below the damaged one will star moving so much to compensate, that you will start having some premature wear and tear of that joint, that leads to degeneration (called osteoarthritis – or OA). Inflammation then sets in there, because mainly of all of the friction created by the extra movement, and this is when you start feeling it. The first sign is usually some diffuse pain around the hypermobile joints (meaning moving too much), especially after prolonged positions (like gardening for a few hours). It can take months, even years after the initial trauma for those signs to show up. And normally, it does not take any special event to trigger it; it will start on its own one given morning and you will wonder what you did so bad to cause you so much pain!

The Discs

The discs are located in between every vertebra of your spine. They provide stability to the joint, allow movement of the spine, and also act as little shock absorbers for your back. A vertebral disc is like a jelly doughnut: the outside (annulus fibrosus) is thick and strong, and the inside (nucleus pulposus) is soft and gelatinous. The disc is maintained in place by ligaments. What normally affect discs are rotational movements, especially if the load on them is heavy (large shoulder and back musculature, fat (overweight), or simply lifting a heavy object). So the worst thing you can do to your discs is to pick up a heavy load, and turn around with it. The pressure put on the disc, along with the rotation, will make the disc want to leave its spot. Fortunately, you have strong ligaments around it that will keep it in place. But if you keep doing it, eventually the ligaments will get tired, give in, and the disc will move out of place. You will then have what is called disc bulging. Once the disc is out, it may limit the joint movement (very painful) and / or put pressure on the nerve root coming out at that level (see below). The next step is the herniated disc, where the nucleus pulposus comes out of the doughnut! No need to say that once you reach that level, it is irreversible damage we are talking about (try to patch a jelly doughnut huh?!).

The Muscles

Back muscles are fairly large, and they cover a lot of surface area. So when they get damaged (muscle strain), they cause some serious pain. A muscle goes into spasm (a reflex contraction) to protect itself from further damage – it is called a protective mode. Spasms hurt (if you have given birth, you know how painful contractions are, and contractions are muscle spasms) and the larger the muscle, the stronger the pain! Muscles normally go into spasm to protect themselves, but they will also do it to protect a segment (a joint, a nerve, a bone…). So it is not impossible that you have muscle spasms if let’s say a disc is out. In other words, muscle spasm does not necessarily mean muscle strain.

Nerve Roots

Nerves cause problems when they either get pulled or trapped. You can pull a nerve when you strain a muscle, since most nerves travel along muscle fibres. But the most common nerve damage is the compression, or the entrapment. The nerve can get entrapped at its exit from the intervertebral foramen (inflammation, bone spur, tumour…anything that may obstruct the tunnel) or can be compressed by a displaced disc or a tight muscle somewhere along the way. Nerves can cause pain, but normally the pain will be felt further along the line, close to the ending of the nerve. Imagine a tree where the trunk is the spinal cord, the branches are the nerves, and the leaves the nerve receptors and transmitters in your extremities. Now if one of the branches get damaged, you will see a scar in the bark, but where will you see a lot of the effects? In the leaves. They will probably turn yellow or show some spots. For the nervous system, it is the same. The brain perceives the damage at the ending of the nerve, and therefore you can have a nerve trapped in your low back and feel pain in your calf from that. Remember, pain is not physical, it is chemical, it is something that your brain perceives and interprets, so depending on your brain, it can be felt in a strange area, or not even be felt at all.

Entrapped nerves can also give you strange sensations like pins and needles, tingling, numbness, heat… and again, generally at the end of the trajectory. So tingling in your toes may mean that something in your back is not well. Interesting huh?!
Definitely the most common nerve to be compressed in the runner’s world is the Sciatic nerve, hence the Sciatica.

The Fascia

The fascia runs all over your body, in one single piece. A lot of nerves run through it. So any damage directly to it or to a surrounding body part may create some tension and the creation of scar tissue. Pain can then be felt directly in the area of the trauma, or further along the nerve. Be aware: fascia is so strong that any change in its thickness may alter your posture and joint positions, creating further damage.

Ligaments

Vertebral ligaments in the low back very rarely get damaged. The muscles around the joints and the limitation of movement by other structures (like ribs) ensure a fairly stable environment for the ligaments. Once they have been strained though, they will allow too much movement in the joint (instability) and probably create a weak link where either the disc can move out of place, or the segment become hypermobile.

Your Posture

Believe it or not, bad posture is probably the worst enemy of your back. It creates muscle imbalance, puts a strain on the ligaments and fascia, and wears out joints by putting them in a bad position where the cartilage is not present or not thick enough. Your sleeping habit is also just as important since you spend 5 to 8 hours in that position (just try to watch television for 10 minutes in some uncomfortable position, them imagine sleeping all night in that position…).

So what to do what to do? In the next publication we will discuss ways of getting rid of most of the above problems.