How the Spine Works

While most back pain is muscular in nature, there are a host of problems that can stem from your backbones. For instance, a slipped disk or herniated disk can be quite painful. Here is an examination of the skeletal structure of the back.

©2006 Publicatons International, Ltd. The complete spinal column viewed from the side.

Spine Basics

In simple terms, your spine is nothing more than a group of bones in a line up the center of your back. The individual bones are called vertebrae. There are 33 bones in all -- 24 vertebrae, the sacrum (which is actually 5 vertebrae fused together), and the tailbone, or coccyx (4 vertebrae fused together). The individual vertebrae are stacked on top of each other from about the level of your belly button up to your head.

When healthy, the bones of the spine are strong and dense. As is the case with all bones, the vertebrae get their strength primarily from two important minerals -- calcium and phosphate. When there is a shortage or loss of these minerals because of an inactive lifestyle (weight-bearing activity actually helps to keep bones strong) or diseases such as osteoporosis, the bones lose their structure and strength. Unless they are weakened in this way or are damaged in an accident or fall, bones do not typically break or wear out.

The spine has four regions. Starting with the neck and progressing down to the pelvis, the regions are the cervical region, the thoracic region, the lumbar region, and the sacral region. All of these regions work together to provide support and stability for much of the weight of the upper body. Each bony level has a passage that forms a tunnel for the spinal cord, thus protecting the spinal cord as it extends downward from the brain.

But the spine is more than just a protective tube. While the spine provides protection and support, its design also allows you to bend, twist, rotate, and otherwise move your upper body in every direction. The bones themselves do not actually bend or twist; the flexibility of the spine comes from structures between the bones called facet joints and intervertebral disks.

Intervertebral Disks

The infamous disks -- technically known as intervertebral disks -- are situated between the bones of the spine, creating a space for nerves branching out from the spinal cord to other areas of the body. The disks are made of tough rings of fibrous elastic material called cartilage; if you sliced a disk horizontally, it would look something like an onion cut through its middle. At the center of the rings of fibro-elastic tissue is a thick fluid with the consistency of very cold molasses.

View of an intevetebral disk showing the pulpy, liquid cneter.

Together, the rings and the jellylike center of the disk act as a shock absorber, much like the shock absorbers on a car. When healthy, they take up much of the shock that walking, running, jumping, and even sitting can place on your spine. Every time you bend, extend, or twist, there is a change of pressure in the fluid-filled area of the disk. In moderate amounts, this change of pressure is actually good for the disks. In the long term, however, excessive forward bending movements -- with the back rounded and the legs straight -- can damage the rings that hold the fluid in place. Unfortunately, this bending motion is one that many people use repeatedly throughout a typical day to reach or lift objects. Even slumped sitting may expose the disks to possible injury.

This damage to a disk starts at the rings in the center of the disk closest to the fluid, and then progresses toward the outermost rings. The condition has often been called a slipped disk. However, the disk does not actually slip out from between the bones. Rather, the fluid begins to break through the rings. When this condition has advanced to the point where there are only a few rings left holding the fluid inside the disk, the condition is known as a bulging disk. The rings can push into the spinal cord or the nerves exiting the cord. If all the rings tear, the disk has ruptured, or herniated.

The three stages of disk herniation. First, a healthy disk with the fluid center in place (left). Second, a bulging disk in which the fluid has begun to break through the fibrous layers (center). Third, the fully herniated, or ruptured, disk where the fluid has broken out of all the layers and leaks into the surrounding tissue (right).

Some people experience a condition called degenerative disk disease. This condition usually progresses over many years. In this process, one or more disks dry out, losing their ability to absorb the loads and shock placed on them with everyday activities. Age also has an effect on the disks in the spine. At age 20, the disks are made up of about 70 percent water. With increasing age, the disks naturally lose their water content.

If a disk wears out, dries out, bulges, or tears, it loses height. This forces the bones closer together, so the facet joints end up having to take much more of the shock as you move. The facet joints, in turn, can wear out prematurely. The loss of height also narrows the opening between the bones through which nerves exit the spinal cord. This narrowing can pinch a nerve, often causing pain.

All of the conditions that affect the disk can, in the later stages, be extremely painful and debilitating. They can interrupt normal work, play, and even sexual function. Taking steps to protect the disks can pay great dividends in the long run. However, most of the time when people "throw out" their backs, it is due to muscle tears or spasms. Learn all about the back muscles in our next section.

Back Muscles and Ligaments

The bones of your spine would not be able to move or even hold themselves upright without the muscles and ligaments that surround them. An important part of understanding back pain is understanding how these structures work and how they can get injured.

Back Ligaments

Attached to all the bones and disks in the spine are long, cordlike structures called ligaments. Not as hard as bone but not as soft as muscle, these bands of connective tissue come in almost every size. Some are short, running only between adjacent bones, but some are very long, extending all the way down the length of the spine.

The ligaments have several important functions. They provide support for the spine from the head down to the tip of the tailbone, holding disks and bones and muscles in their proper places. Their main function is to hold the bones together, allowing bending, twisting, and other movements to occur within safe ranges. Because ligaments are somewhat elastic, giving them the ability to stretch a little but not too much, they are perfectly suited for this task. When you bend over forward as far as you can, these ligaments reach the end of their length; they become taut, keeping the bones from moving apart any farther. This is an important function, because it spares other parts of the spine, such as the disks, the burden of holding the bones together -- a damaging task that they are simply not designed to do.

When you are standing straight, the ligaments are at normal length (left). However, when you bend, rounding your back, the ligaments are stretched to their maximum length trying to hold the bones together and support your hanging upper-body weight (right).

The ligaments also play a major role in posture. When they maintain their normal length and flexibility, they support the bones of the spine, keeping them in good positions. With poor postural habits, however, the ligaments on one side of your spine can be overstretched. Over time, probably months or years, the result is poor posture. Poor posture, in turn, can cause the ligaments to ache. Indeed, back or neck pain that cannot be attributed to a specific accident or injury is often a sign that poor posture is taking a toll on the ligaments. The ligaments, when sprained or torn, take a long time to heal because of their poor blood supply.

Back Muscles

Muscles are cordlike structures that are even more elastic than ligaments. Like ligaments, muscles can stretch; unlike the ligaments, muscles also have the ability to contract, or shorten. This is, in fact, what happens when you lift a cup of coffee, throw a ball, or do anything that requires movement of the body. The muscles shorten and lengthen, pulling the bones in different directions to coordinate our movements. When you lift, lower, push, pull, carry, or perform any activity, the muscles are doing the work.

Muscles also work to keep the body from moving when movement is not desired. For example, if you are sitting in a canoe and the canoe starts to tip to the left, your muscles quickly respond by coordinating your body's movement to the right to maintain your balance.

Muscles are true workhorses and can be your back's best friend. When conditioned, your muscles maintain their strength, endurance, and flexibility, which allows the body to move and work with less risk of injury and pain. When working properly, the muscles can greatly reduce the load on the bones, facet joints, disks, and ligaments. In contrast, when the muscles become deconditioned from lack of use or from injury, they tend to lose their size, strength, endurance, and flexibility.

How do muscles work? Basically, when you want to move, your brain sends a message through the nerves to the correct muscle. When the message gets to the muscle, chemicals inside the muscle cause the muscle to shorten. Because the muscle is attached to the bone, this shortening pulls on the bone. If the strength of this shortening is strong enough, the bone, and therefore the body, moves.

When your back muscles are in shape, they support the spine well (left). When they are weak, the spine can suffer poor posture and possible injury (right).

To lengthen, or relax, and return to its resting position, the muscle requires energy. If the muscle runs out of energy, or becomes fatigued, cannot relax back to its original length. The end result may be what is often called tightness. As you use them, some of the smaller muscles in the back may start to get tired and shorten. When the muscles shorten, the bones are held together more tightly than normal; this constriction, in itself, can cause back pain and limit your ability to move with full flexibility. In fact, many people have back pain that is probably related to tight, deconditioned muscles that have fatigued and shortened.

In the short term, this muscle fatigue may result in nothing more than a little low-level back pain, but if this condition continues day after day, year after year, the back can wear out much faster than it should. If the muscles are not stretched, they can be injured. If you're lucky, the injury will only be a muscle pull or strain, in which the muscle is only slightly torn. Muscles can, unfortunately, be damaged more severely. The good news is that muscles, because of their good blood supply, tend to heal fairly quickly.

Our final stops on this tour of the back will be the facet joints and the nerves. Then, once we have all the parts laid out and explained, we will tell you how they all work together. Keep reading to learn more.

Facet Joints and Nerves

We're almost done explaining the anatomy of your back. All we have left are the facet joints, or how the bones of the spine fit together, and the nerves -- don't forget, the back also holds a major part of the body's central nervous system.

Facet Joints

Most of the bones of the spine have four joints, or places where they rub directly against other bones. These joints are called facet joints. Located on the extensions of bone off the back side of the vertebrae, these surfaces come in contact with those of the vertebrae directly above and below. Their purpose is to safely guide and restrict the movement of your spinal bones.

To get an idea of how the facet joints function, think of a door and doorstop. When a door opens so far that it hits against the stop, no further movement in that direction is allowed. In your spine, the bones move as far as the facet joints will allow them to before one bone forces another to stop. For example, when you stand and put your hands on your hips, bending as far backward as you can, it is the facet joints that help stop your backward movement. The same thing goes when you rotate your neck or back to the left or right as far as you can.

Located on the bony extensions of the vertebrae, the surfaces of the facet joints fit together like a three-dimensional puzzle.

The surfaces of these joints, when healthy, are relatively thick, hard, and slick. This combination allows the bones an easy, pain-free gliding movement. However, if the joints are irritated, injured, or not used often enough in physical activity, the joint surfaces become thinner, softer, and almost sticky. This results in more difficult movement and possibly pain.

Without intervention, this condition can become chronic; bone spurs may even develop. Bone spurs are the bones' way of trying to grow together, or fuse, rather than remaining separate and moving freely. This condition can be extremely painful and may require surgery. However, it doesn't take such a serious condition to make these joints painful. If you've been standing on your feet too long, the facet joints end up getting compressed by the effects of gravity and the strain of supporting your upper-body weight, causing low-back pain even in healthy backs.

Nerves

In the spaces between vertebrae run the nerve roots—exits off the spinal cord's information highway.

Any discussion of the spine is not complete without talking about the body's messenger system -- the nerves. In simple terms, the nervous system is similar to the electrical wiring in your home. The wiring system in your home carries electricity from room to room. The nerves carry electricity -- in extremely small amounts -- around to the different parts of the body.

The nerves actually begin in the brain, your body's command center, and branch out through the spinal cord, which runs through the bones in your spine. The spinal cord is the main information highway in your body; all of the brain's signals to the body are carried through the spinal cord. Where the nerves branch off and leave the spinal cord, they are called nerve roots. Beyond this point, they are simply known as nerves.

The brain is always monitoring what is happening throughout the body and sending messages -- tiny amounts of electricity -- through the nerves. The various parts of the body can, in turn, send signals back to the brain regarding their condition. The feedback to the brain includes important sensations such as pressure, heat, cold, movement, and the big one, pain. If damage occurs to the nerves, communication breaks down, and many problems can arise with the organs that require instructions or that need to report sensations.

Clearly, the spinal cord is vital to the functioning of your entire body. All of the sensations and all of the organs from your neck to your toes rely on that one telephone line. The other structures of the back (bones, muscles, and ligaments) can protect this pathway if they are properly maintained, but poor posture and bad habits can weaken your back's protective ability. Indeed, sometimes injury or strain to a muscle or disk can even affect the nerve root or cord itself, actually causing a nerve injury. And damaged nerves are not only bothersome -- they hurt!

Putting It All Together

All of these spinal structures and tissues work together to allow you to bend, move, or do essentially anything. It is a complex system with complex functions. Not only does your back have to support a good deal of your body's weight and carry vital nerve signals to all of the parts of the body, but we ask it to bend and twist at the same time. It is an engineering marvel.

Even though your back is very versatile, it does like certain positions better than others; that is, it can tolerate some postures or poses better. Specifically, the back is most comfortable while lying down with its natural curves aligned. In general, for sitting or standing, the more you can keep your curves properly aligned, the better it is for your total spine.

Moving, bending, and twisting in limited ranges is healthy for all parts of the back. Limit the forward bending of your back to about 30 degrees; this is a fairly safe range. A similar range exists for twisting of the back; you should try to minimize twisting motions to each side. Remember also that staying for extended periods of time in bent, twisted, or any awkward positions dramatically increases the physical stress placed on the spine. Certainly, the worst thing you can do to your back is combine all of these single factors by repeatedly bending over with straight legs and a rounded twisted back, then picking up something heavy at arm's reach, and then staying in this position for an extended period of time.

Your spine and the related structures do benefit from movements that place acceptable levels of stress on them. Proper exercises can thicken, stretch, lubricate, and build the endurance of your back and strengthen its ability to withstand the forces of gravity in all of your movements. The most benefits are derived when these healthy movements are performed regularly. On the other hand, some people have problems with their backs because they have overdone it. They have performed the same movements too many times, and overuse has fatigued or injured certain spinal tissues.

However, no matter how many precautions you take, we all injure our backs now and again. If you have just injured your back -- maybe by lifting something that is too heavy -- our next page will give you some tips for dealing with the pain immediately after the incident.

Emergency Back Pain Relief

The following remedies are appropriate for anyone who is suffering from back pain due to tight, aching back muscles or a strain. However, if you are experiencing pain, weakness, or numbness in the legs, or a loss of bowel or bladder control, see a doctor without delay.

The best cure for an aching back is a little rest.

Rest Your Back

It is almost impossible to do anything without using your back. Even activities that do not seem very stressful on your back usually require some effort on its part. The activity need not be very demanding in terms of muscle strength to cause a problem; maybe the activity is one that your back just isn't used to. Often your back muscles simply overdo it. The end result may be a muscle pull or strain. In fact, most back pain and the majority of back injuries are probably related to muscle pulls and strains.

When strained, your muscles need a chance to turn off, rest, and begin to heal themselves. Continuing to be too active can further aggravate a sore back. Find a comfortable position to allow your back to rest. The best position for an injured or achy back is lying down on either your back or side, with the curves of your spine aligned in their natural position. Try lying down on a firm surface like a padded, carpeted floor. You can relax your back by placing a couple of pillows under your knees. If on your side, place the pillows between the knees instead of under them. For your neck's comfort, roll up a small hand towel and place it under your neck to give it a break, too.

Apply Ice to Reduce Swelling

Immediately after your back is injured, blood rushes into the damaged area. Even though swelling is part of the body's normal healing process, too much inflammation can increase pain and lengthen your recovery time. Applying ice immediately after a strain reduces the amount of inflammation, speeds up the healing process, and can numb some of the pain.

Generally, unless otherwise instructed by a physician, ice should be used instead of heat for the first 48 hours after a back strain. Heat from a hot shower, heating pad, or some popular topical lotion may feel better than using ice, but heat treatments increase blood flow, causing greater inflammation, more pain, and usually a slower recovery. At least for the first two days, stick with ice.

You do have to be careful with ice also, though. Incorrect application of ice can damage the skin. To apply ice correctly, warm a towel or pillowcase in slightly hot water, wring out the water, and quickly place an ice pack, ice cubes, or crushed ice in it. Immediately place the towel or pillowcase over the strained area of the back for no longer than 12 to 15 minutes.

If you do not have a towel or pillowcase handy, freeze water in a small paper cup. Peel the cup back so that the ice can go directly on the skin. Make sure that you continually move the ice around in circular motions, not allowing the ice to sit in one place. Another method is to place the ice in a plastic bag or some plastic wrap before applying it to the skin. For additional benefits, use repeated ice treatments approximately once every hour for the first 24 to 48 hours after the strain. This should help to keep swelling to a minimum and reduce the related pain.

Compress the Area

Gently compressing an injured area can assist ice in reducing inflammation and pain, while speeding recovery. Compressing the muscles can provide some temporary support for the area, which may allow you to move around more easily while making you more comfortable. Try using an elastic bandage; wrap it around your midsection over the strained area of the back. Make sure you do not wrap it too tightly. (The wrap can be used over an ice pack providing the ice is applied as described in remedy 2 and for no more than 15 minutes.) An alternative to the elastic bandage is a back support, which acts like a corset to compress and support the back and stomach muscles.

Take Two Aspirin

An over-the-counter analgesic my help relieve your pain.

Taking an over-the-counter analgesic such as aspirin, acetaminophen, or ibuprofen may help relieve your pain. However, be aware that not all medications, not even nonprescription ones, are for everyone. Pregnant women, for example, should not take any medication without first checking with their doctor. And people with ulcers should stay away from analgesics containing aspirin. Don't take any medicine for a bad back without first learning about its potential side effects and talking to your doctor. For a list of precautions to take when using over-the-counter analgesics, click here.

Know When to See a Doctor

Muscle pulls and strains, although quite common, can be severe. Other spinal tissues can also experience injuries. Ligaments can be sprained or torn, joints can become irritated, and of course, spinal disks can bulge and tear. It is important for you to know when a back injury goes beyond your ability to treat yourself.

After a strain or injury to the back, the body can have a variety of natural reactions causing numerous symptoms, such as back pain. If, after two or three days of bed rest, your severe back pain has not subsided, you should see your physician. Sometimes, when many of the tissues in the back are seriously injured, the muscles can tighten up, or spasm, and clamp down around blood vessels. Muscle spasms can cause pain, sometimes severe, that makes it difficult to sit, stand, or do virtually anything. Many times, the only way to relax intense spasms is with the assistance of a physician.

Other signs to watch for are the loss of bowel or bladder control or pain, numbness, tingling, or other similar sensations that run down an arm or leg or around the chest. This type of symptom can make your hands, fingers, feet, and toes feel like they are burning, cold, asleep, or being poked with pins and needles. Finally, it's time to see your physician when it takes larger and larger amounts of medication to reduce your back pain.

If you experience any of these symptoms, get a professional opinion. Serious injuries that go untreated or are treated incorrectly can be dangerous, leading to further impairment and possibly irreparable damage. Just having one of these symptoms does not automatically mean that you will require major therapy. However, it's best to let your physician rule out serious spinal problems so that you can put your mind at ease and get on with the business of healing.

If you follow these steps you should be able to reduce some of your discomfort and reduce the swelling in your back. If, however, you are experiencing a long-term problem, the next section will offer you some solutions to relieve your backaches.

Chronic Back Pain Relief

Some people can have a sore or aching back for weeks or even months at a time. If you've had chronic back pain like this, maybe some these tips can help.

Alternate Heat With Stretching

Muscles often spasm, or get tight, as the result of a back injury. This can be quite painful. Tight muscles and most sore joints do respond quite well to heat (topical lotion, hot shower or bath, heating pad), because the warmth relaxes tight muscles, increases blood flow, and eases pain.

Tips for Stretching Back MusclesHere are some hints for safe effective stretching: Take your time; stretch slowly and gently. Never force your stretch past the point of mild tension. Hold the stretch for at least ten seconds. Never bounce a stretch. Relax your muscle completely between stretches. Repeat the stretch several times throughout the day.

Gently stretching these muscles after the heat application can further relax and lengthen tight tissues, easing movement and reducing pain. Remember, though, in an acute injury, don't use heat until after 48 hours, because it can increase the swelling and slow your recovery. In the first 48 hours after an injury, ice is the better alternative, and ice can also be used with stretching. Ice works a little bit differently than heat; it tends to numb the sensation of pain in sore muscles, which allows you to stretch and relax tight muscles gently.

The use of heat or ice is a personal choice, and you have to experiment with each to determine which works best for your particular strain or injury. Try applying heat or ice as suggested for 10 to 15 minutes, and then see if performing the stretches helps your back pain subside. Be careful not to overstretch. Overstretching can aggravate a bad back, increasing pain and possibly causing re-injury. To stretch correctly, take a stretch only to a point of mild tension, not pain. Hold the stretch at this point for at least ten seconds, making sure that you do not bounce on the stretch. Relax the stretch and repeat right away two or three times.

Your muscles are kind of like springs. They tend to stretch fairly easily if you stretch correctly, but they tend to come back to their shortened position over the course of a few hours. So you will probably have to repeat these stretches throughout the day. Finally, if your pain or symptoms increase, stop the activity and consult with your physician or therapist.

Avoid Harmful Activities

The body starts its healing process as soon as an injury occurs. You can help this process by avoiding activities that might make your back condition worse. Depending on the degree of damage to your back, many activities you perform on a daily basis can be stressful to an already sore back. When your back is recovering from a strain or injury, you should consider avoiding or at least being extra careful with the following activities.

Avoid obviously stressful activities such as shoveling, in which the back is often twisted while lifting the weight of the shovel and its contents. Loading and unloading groceries from the back seat or the trunk of the car can quickly irritate your back even if the groceries don't weigh too much. In the same vein, be careful picking up children. It can be very easy to forget how heavy a small child is. Also, hoisting a toddler up to give him a hug is not usually considered strenuous work, so you may not realize the potential hazard it presents to your back.

You also must watch out for less strenuous activities that you might not associate with back stress and pain. Not every movement that is dangerous comes with an obvious warning sign. For example, chores such as raking or vacuuming can be very stressful to the spine, because reaching causes the spine to rotate, a motion that an injured spine may not be ready to do. Even doing the laundry, especially bending to remove heavy, wet clothing from the washer, or washing the dishes can wreak havoc on a painful back.

As your back starts to heal, gradually add these activities back into your daily life as your back can tolerate them, but remember, your back takes time to totally rebuild its strength and stamina after a strain or injury. Don't rush it.

Try a Massage

Your muscles operate kind of like your car's engine. As they work, muscles accumulate waste products that need to be removed like the exhaust from your car's engine. If these waste products do not get out of the muscles promptly, then the muscles don't work very well. Furthermore, the buildup of these waste products can even create pain. A gentle back massage helps to relax tight muscles, open blood vessels, and flush out these waste products, allowing the muscles to work normally while reducing pain and stiffness. Using an over-the-counter topical lotion that contains a heat agent such as mentholyptus can further increase blood flow and comfort by enhancing the relaxation of muscles and blood vessels; follow the package directions.

A gentle massage helps to relax tight muscles and open blood vessels.

Practice Good Posture

Couches and recliners can feel very comfortable; however, very few are designed with the health of your back in mind. If you are going to sit, try not to slump or slouch. Poor posture, such as slouched sitting, can place a great deal of stress on your muscles, ligaments, and disks. This stress can make it more difficult for proper healing to occur and may increase back pain. Choose postures and positions that allow you to keep the curves of your back aligned. Try rolling up a towel to about the size of your forearm and placing it in the small of your back to support the curve of your low back. If this feels uncomfortable, see if rolling it smaller helps. Remember to support your neck, as well.

Keep Moving

Even though rest is important for an injured back, too much rest can actually make your back worse. Let's say you have hurt your back, so you lie down on your back on the floor or couch or in bed for a week. Your decision to lie down may have been a good one in the short term -- for a few hours or even a couple of days. The rest will allow your back to heal. In the long term, however, lack of movement robs the spine of its health.

After a couple of days of inactivity, even healthy muscles start to lose their strength and flexibility -- they begin to atrophy. The longer you are immobile, the greater the loss. But muscles are not the only ones who suffer. Movement is vital to the other structures of the back, also. The intervertebral disks receive their blood supply from the bones above and below when you move. Inactive bones that are not bearing any weight become weaker and more brittle. So in essence, movement strengthens and feeds your spine, whereas inactivity weakens, starves, and decreases its life span.

Although your back may need short periods of rest in a sitting or lying position, you should try to change your position from lying to sitting or even walking if you can tolerate it. While you're lying down or sitting, try engaging in an activity that requires the gentle use of your hands and arms, such as knitting or some other handiwork. Whether you know it or not, using your arms, hands, or even your feet in this way is actually a low-level back exercise that will strengthen and feed your spine.
As your condition improves, increase the amount of time that you spend on your feet, performing light activities that require limited bending and twisting movements. Be especially careful with lifting and lowering activities. Gradually progress toward activities that include the bending, limited twisting, and light lifting that your back can tolerate.

Now you should have a fairly comprehensive understanding of how your back works and the ways you can injure the various parts. Of course, knowing how you injure you back won't necessarily stop you from doing it. Fortunately, you now know how to relieve back pain and when you should see a doctor.