Why Does My Lower Back Hurt?

Your lower back, which spans from the bottom of your rib cage to the top of your legs, is a hardworking thing. It supports the weight of your upper body. About 80% of people have low back pain sometime in their lives.

That area of your body has a lot of moving parts that can cause trouble:

  • Vertebrae. These five bones are numbered L1 through L5 (“L” stands for “lumbar”).
  • Disks. These spongy structures between the vertebrae cushion the bones as your body moves.
  • Ligaments connect the vertebrae and keep them in place.
  • Tendons connect your muscles to your spinal column
  • Nerves. Among them is the sciatic nerve, the longest in your body.

Types of Low Back Pain

If your back pain is short-term -- meaning it lasts a few days or a few weeks -- doctors call it “acute.” If it has gone on for 3 months or more, it’s considered chronic.

You may hear the term “mechanical” low back pain. That means the problem involves the moving parts of your back -- disks, vertebrae, ligaments, tendons, and muscles.

Other names for low back pain include lumbar syndrome and lumbago.

How your back pain feels can vary. You might describe yours as:

  • Aching
  • Burning
  • Sharp
  • Stabbing
  • Dull
  • Vague

It may also radiate down into your butt, hips, or thighs.

What Causes Low Back Pain?

It might develop suddenly, like after you lift something heavy. Or it might come on slowly.

As you get older, the structure of your back begins to show wear and tear. Doctors call it “spondylosis,” which means your spine’s joints, disks, and vertebrae get worse over time. This slow decline can lead to many problems, like the following:

  • Strains. This means you overstretch or tear your tendons or muscle. You can do this by twisting, lifting something that’s too heavy, or lifting something the wrong way.
  • Degenerated disks. When these are healthy, they cushion your back as you bend, flex, and twist. As disks begin to wear out, they no longer absorb the shock of these movements well.
  • Herniated or ruptured disks. Normal disks are rubbery. When they become squeezed, a portion bulges out between your vertebrae.
  • Radiculopathy. A spinal nerve can become pinched or inflamed. This can cause low back pain to travel (radiate) down your legs. It can also cause numbness or tingling.
  • Sciatica . This is the type of radiculopathy that affects the sciatic nerve, which runs from your butt down the backs of your legs. When it’s inflamed, you may feel burning or pain like an electrical shock that may go all the way down to your feet.
  • Spondylolisthesis. In this condition, a vertebra slips out of place and pinches spinal nerves.
  • Spinal stenosis . Your spinal column may narrow over time, putting pressure on your nerves. Your legs may feel numb and grow weaker.

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Sometimes, back pain is caused by a long-term, underlying condition. Possibilities include:

Back pain can also be a sign of a serious underlying condition that needs attention right away. For example:

  • Infections of your vertebrae (osteomyelitis), disks (discitis), or the joints that connect your spine to your pelvis (sacroiliitis)
  • Abdominal aortic aneurysm (when the blood vessel that supplies your belly, pelvis, and legs becomes swollen)
  • Kidney stones (pain in the lower back, usually just on one side)
  • Tumors (though this is rare)

Fewer than 1% of people with low back pain will turn out to have a serious problem like cancer or an infection.

Who’s at Risk?

Certain things make it more likely that you will have low back pain:

  • Age. Most people first have trouble with their backs between ages 30 and 50, and the problem gets worse as they get older. That’s mostly because of wear and tear.

  • Being out of shape. If your abdominal and back muscles are weak, they don’t do as good a job of supporting the structure of your spine. You’re also more likely to hurt your back if you suddenly ramp up your exercising after you’ve been inactive.

  • Obesity . Extra weight puts a strain on back muscles.

  • Pregnancy . Your pelvis is changing, and so is the way you carry weight. Back problems usually go away once your baby arrives.

  • Genetics. Some underlying causes, like inflammatory diseases, are inherited from one of your parents.

  • Your job. If you have to lift, push, pull, and twist at work, you may be at risk for more back pain. But desk jobs come with their own set of problems. If you sit at a computer all day, you may have back pain, especially if you have poor posture.

  • A heavy backpack. Put your child’s school backpack on the scale. If it weighs more than 20% of his weight, it’s too heavy and could cause muscle strain and back pain.

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When to Call the Doctor

Most back pain gets better after a few weeks. But you should call the doctor if:

  • Your pain is constant or intense, especially at night or when you lie down.
  • Your pain spreads down one or both legs.
  • You feel numbness or tingling in one or both legs.
  • You’re losing weight without trying.

Go to the emergency room right away if you have any of these symptoms:

WebMD Medical Reference Reviewed by Lisa Bernstein, MD on October 13, 2016

Sources

SOURCES:

National Health Service (U.K.): “Back Pain Guide.”

National Institute of Neurological Disorders and Stroke: “Low Back Pain Fact Sheet.”

Johns Hopkins Health Library: “Diseases and Conditions -- Low Back Pain.”

Cleveland Clinic: “Chronic Back Pain.”

Mayo Clinic: “Back Pain.”

American Academy of Pediatrics: “Backpack Safety.”

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