Causes of Unexplained Chronic Back Pain

Medically Reviewed By William C. Lloyd III, MD, FACS
Was this helpful?

If you’re accustomed to wincing and muttering “oh, my back,” on a regular basis, then you know how annoying and frustrating chronic back pain can be.

How did the back pain start? For many people, it’s the result of an injury that strains tendons or muscles or stretches a ligament in the back, perhaps from a car accident, from picking up a heavy object, or even from an overly-ambitious gym session. Ouch. That initial pain is called the acute phase. Sometimes it goes away but for some people, it lingers on and becomes a chronic problem.

But injury or trauma aren’t the only culprits for chronic back pain.

Inflammation of the area where the spine joins the pelvis is the hallmark of a condition called ankylosing spondylitis (AS), which is a progressive form of arthritis. It’s not always a severe diagnosis, but people who develop ankylosing spondylitis may experience ongoing pain and even the loss of flexibility of their spines. In the most severe cases, two or more bones in the spine may fuse together as the result of long-term inflammation. People who suffer from AS often have inflammatory symptoms elsewhere in the body, including the eyes, skin, intestines and lungs.

It’s also possible that your back pain is caused by a more serious underlying condition, such as an infection or tumor. But it’s unlikely, statistically speaking. According to the National Institute of Neurological Disorders and Stroke, most low back pain is mechanical in nature. Here are some other possibilities:

  • Herniated or ruptured discs. Discs are the rubbery cushions that occupy the spaces between each vertebrae that make up your backbone. If a disc tears or bulges out of its usual location, it can put painful pressure on your spine. This can happen as a result of injury or from the wear and tear that our bodies experience as we age.

  • Sciatica. If you’ve ever experienced shooting pain that radiates down your lower back and down one side of your buttocks, you’re familiar with sciatic nerve pain. Sciatica is often caused by one of those herniated discs pressing on the roots of your sciatic nerve. According to the American Academy of Orthopedic Surgeons, 80 to 90% of cases tend to resolve over time without the need for surgery.

  • Disc degeneration. Even if you don’t experience a herniated disc, the standard aging of those cushions can still cause back pain. Discs tend to dry out and become less flexible as we get older. The discs shrink and weaken as part of the normal aging process.

  • Spinal stenosis. This condition, which tends to affect people over 50, occurs when the open spaces in the spine begin to narrow and put pressure on the spinal cord and nerves. It causes back pain, but it can also cause numbness, weakness or tingling in your legs.

  • Scoliosis. An s-shaped curve in your spine typically develops in childhood, but it can develop in adulthood too, often resulting from the combination of age and deterioration of the spine. The curve itself doesn’t really cause the pain—it’s the deterioration that makes your lower back ache or throb. That deterioration and the deformity in your spine can put enough pressure on your nerves to cause pain, weakness and numbness in your legs, too.

Consult your doctor about your back pain, especially if you’re not sure about the cause. It might be time for some closer examination, which could lead to more targeted treatments—and hopefully, some relief.

Was this helpful?
Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Sep 12
View All Ankylosing Spondylitis Articles
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
  1. Sciatica. American Academy of Orthopaedic Surgeons.
  2. Herniated Disk in the Lower Back. American Academy of Orthopaedic Surgeons.
  3. Degenerative Adult Scoliosis. University of Maryland Medical Center.
  4. Spinal Stenosis. Mayo Clinic.
  5. Questions and Answers about Ankylosing Spondylitis. National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS).
  6. Low Back Pain Fact Sheet. National Institute of Neurological Disorders and Stroke.