October 15, 2018
What Causes Back Pain?

What Causes Back Pain?

by Berkeley Wellness

There are myriad possible causes of back pain. However, all back pain falls into one of three major categories: nonspecific low back pain, radiculopathy and “other.” Nonspecific low back pain (also called simple low back pain, lumbar strain and lumbosacral strain) is by far the most common. As its names suggest, the precise cause in a particular case is usually not known. Nor does the cause need to be known in order to manage it effectively, either by yourself or with the help of your doctor. That’s because an important feature of nonspecific low back pain is that it doesn’t cause symptoms characteristic of the other kinds of back pain (that is, radiculopathy or “other”).

Nonspecific low back pain may come on slowly, hours after strenuous physical activity involving the back. This kind of pain is usually described as “achy” and is often associated with back stiffness. More commonly, nonspecific low back pain appears suddenly, often for no apparent reason, although it may be associated with lifting or bending. The pain is located in the low back, and it may radiate to the buttocks or thigh (most commonly on one side only). If the pain comes on suddenly, it is initially usually fairly severe and sharp, but then fades rapidly to a dull ache or even no pain at all, unless you subsequently move the wrong way, in which case you again experience the transient severe pain. Particularly at the beginning of an episode of nonspecific low back pain, you may be unable to move comfortably from lying to sitting or sitting to standing, and you may be unable to stand fully upright.

Nonspecific low back pain usually doesn’t radiate below the knees. If your pain radiates below your knees, or if there is any numbness or tingling in the calves or feet, you should see your doctor to make sure your pain isn’t something other than nonspecific low back pain.

Nonspecific low back pain never causes numbness or tingling in the groin and genitals, muscle weakness or urinary or fecal incontinence. If you have any of these symptoms, you should immediately call 911, because you may have cauda equina syndrome (see below), which is a medical emergency.

The following conditions can, to varying degrees, be sources of back pain. (They may also cause symptoms that are not limited to back pain.)

Strains and sprains

A sprain is defined as an injury in which a ligament (the tough, fibrous tissue that connects bones to other bones) is stretched or partially torn, whereas a strain occurs when a muscle or tendon (the tissue that connects muscle to bone) is stretched beyond its normal range. It can be difficult to discern a strain from a sprain. Both may result in painful muscle spasms, as well as bruising, swelling and painful movement.

Degenerative changes

The vertebrae, intervertebral discs and the facet joints connecting the vertebrae are all subject to degenerative changes as a consequence of normal aging. You might say our body parts simply start to “wear out” after years of use. Diagnostic imaging studies have shown that such deterioration usually begins fairly early in life—around age 20, and sometimes even younger.

Herniated disc

Again, normal aging will almost invariably degrade the structural integrity of the intervertebral discs. The outer membrane of the disc becomes thinner and prone to microscopic cracks or tears. Furthermore, the central portion of the disc dries out and flattens as it gradually loses water content over the years. Discs that are weakened as such are at risk of herniation—that is, the development of a weak spot in the outer membrane, so that the gelatinous tissue in the center bulges out through it. Pain results from pressure on a spinal nerve from the protruding hernia, as well as from the release of chemicals that further irritate the nerve.

Autopsy studies reveal that the vast majority of people develop a herniated disc at some point in their life, but only about 10 percent of the population experience pain from it. The symptoms resulting from a herniated disc depend upon which spinal nerves are affected. Pain can occur not only at the site of the herniation, but also in the part of the body served by the nerve that’s involved. For example, a pinched nerve in the cervical spine can cause neck pain in addition to pain that radiates down the arms, or symptoms of weakness, numbness or tingling in the arms or hands. Likewise, a herniation in a lumbar disc can cause pain, weakness and numbness that radiates down the sciatic nerve into the buttocks, thigh, calf and/or foot (sciatica). A herniated disc is one of the most common underlying causes of sciatica (see below for more).

Pain from disc herniation often comes on suddenly, commonly after feeling “something snap” while bending or lifting (or even something mildly traumatic, like sneezing). The pain may be only moderate at first and increase in intensity over time. It’s possible for any disc along the spine to become herniated, but in 90 to 95 percent of cases, one of the two lowermost lumbar discs is involved, as these discs bear the most weight.

Bone spurs

In response to years of wear and tear from supporting the body’s weight, the bones of the spine may begin to form bone spurs (osteophytes). The colloquial term “bone spurs” is actually somewhat misleading, as the word “spur” suggests that these bony growths are sharp and jagged in nature, and stab into other tissue. In fact, osteophytes are smooth structures that form over time, and are exceedingly common among people over 60. Osteophytes can indeed press on spinal nerves and cause pain, but most often they produce no symptoms.

Vertebral compression fractures

The vertebrae are normally very strong, durable bones, able to bear a lot of weight and strain. But certain disorders can weaken the bones throughout the body, and the bones of the spine can become particularly vulnerable to compression fractures.

The most common underlying cause of vertebral compression fractures is osteoporosis (“porous bones”), a condition in which the bones have lost enough of their density and structure to be fragile and at high risk for fractures. The process of bone mineral density decrease is usually gradual, but it is accelerated by menopause and prolonged use of certain medications, mainly glucocorticoids (“cortisone” preparations). Normal, healthy bone tissue goes through cycles of being broken down and built back up, with strong new bone cells replacing the old. Paget’s disease causes a disruption in this process that results in breakdown of bone tissue and the formation of new but weaker, chaotically structured bone that is subject to fracture.

In contrast to osteoporosis, which affects all the bones in the body, Paget’s disease usually affects only particular bones, the specific ones differing from individual to individual. The bones of the spine, pelvis, skull and femur (thighbone) are especially vulnerable. Paget’s disease is the second most common bone disorder (after osteoporosis) in elderly people. The majority (70 to 90 percent) of people with Paget’s disease have no symptoms. Hyperparathyroidism (a disorder in which the parathyroid gland produces excessive amounts of parathyroid hormone) can affect the skeletal system by accelerating the normal breakdown of bone tissue (without the compensatory building up of new tissue) and by depleting the body’s calcium stores. Compression fractures may result.

Certain kinds of cancer (especially breast and prostate cancer, and multiple myeloma) may spread to the spine, causing structural weakness and compression fractures.

Spinal stenosis

Another common cause of back pain among people beginning in their 50s is spinal stenosis. Stenosis comes from the Greek word for “choking,” and spinal stenosis refers to a narrowing of the spinal canal through which the spinal cord runs.

Narrowing of the spinal canal is part of the aging process, and predicting who will become symptomatic from it is not possible. Narrowing sufficient to cause the symptoms of spinal stenosis usually occurs in either the neck or low back region. As bone tissue impinges on the nerves of the spinal cord, pain may result. In many cases, spinal stenosis occurs when degenerative changes in the spine allow bone to rub against bone, which can lead to the formation of bone spurs. These bone spurs can take up space within the spinal canal and exert pressure on spinal nerves or the cauda equina (the aforementioned horse tail–shaped nerve bundle at the base of the spinal cord). Spinal stenosis also can occur in combination with disc herniation.

Symptoms may range from minor numbness, tingling or weakness in the legs (especially while walking or standing) to excruciating pain and loss of urinary or fecal continence. Pain tends to be mild at first, gradually becoming more intense. Symptoms may manifest as pain and numbness radiating through the buttocks and into the legs, often with a feeling of cramping and weakness in the legs, producing a “rubbery sensation” that may increase the risk of falls. Lumbar spinal stenosis is the most common preoperative diagnosis for adults over 65 undergoing spinal surgery.

Spondylolisthesis

The term “slipped disc” is colloquial and misleading. It is used in the vernacular to refer to a herniated intervertebral disc (described above)—but with herniation, no actual “slippage” is involved. Yes, the soft tissue between two vertebrae has been structurally compromised, causing it to bulge outward (or even break into fragments), but the disc hasn’t actually “slipped” from its place between the vertebrae. With spondylolisthesis, however, a vertebra actually does slip out of its proper position relative to the adjacent bones in the spine. When this occurs—commonly the result of physical trauma or, in later years, age-related degeneration—it is usually the fourth or fifth vertebra of the lumbar spine that is affected. The facet joints connecting the vertebrae can become inflamed and may impinge upon spinal nerves, causing pain. Spondylolisthesis can cause pain in the lower extremities (sciatica) as well as in the back.

Vascular claudication

The symptoms of spinal stenosis are similar to those of vascular claudication, a condition that results from an entirely different cause—namely, atherosclerosis (narrowing or “hardening” of the arteries owing to the buildup of arterial plaque), which restricts blood flow to the legs. Although both stenosis and vascular claudication cause sensations of weakness, cramping and pain in the legs while walking, there are differences in the ways in which these symptoms manifest. The pain of vascular claudication begins to subside immediately with rest, even while still standing. In contrast, pain from spinal stenosis often persists while standing, and even after lying down or changing posture to relieve symptoms, the pain tends to subside more slowly than that caused by poor circulation. Another difference: the pain of spinal stenosis begins in the back and radiates downward into the legs; the pain of vascular claudication begins in the calves or feet and radiates upward.

Spinal deformities

Spinal deformities that affect the natural shape or curve of the spine are likely to appear early in life, but tend to become more pronounced with age. One common type of spinal deformity is kyphosis, also known as “hunchback” or “dowager’s hump.” It usually affects the upper (thoracic) portion of the spine, producing an exaggerated hunched or bent-over, forward-leaning posture. In more rare instances, it can affect lower regions of the spine, too. It is most common among women and may result from disc degeneration, cumulative vertebral compression fractures (often associated with osteoporosis) or a combination of both.

Scoliosis is another common type of spinal deformity. It is characterized by a sideways bend or twist in the spine that produces biomechanical problems and pain that vary according to the severity of the abnormal curvature. Scoliosis is typically diagnosed in childhood or adolescence, but it may develop or worsen in adulthood, owing to degenerative changes in the spine.

Cauda Equina syndrome

When the cauda equina (the nerve bundle at the base of the spinal cord) is affected by nerve compression owing to disc herniation, spinal stenosis or other degenerative changes in the spine, the result may be a sudden onset of bowel and/or bladder problems (incontinence or, conversely, the inability to void completely), numbness, tingling or pain in the groin, buttocks or legs, and/or severe muscle weakness in the legs. These symptoms constitute a medical emergency known as cauda equina syndrome. If you experience such symptoms, you should get to a doctor or emergency room immediately.

The Radiating Pain of Sciatica

Sciatica is pain that originates in the lower back or buttocks and radiates down one thigh to below the knee, usually into the foot. The pain is often persistent and more severe than a run-of-the-mill backache.