Ankylosing spondylitis (ank-kih-low-sing spon-dill-eye-tiss) is a chronic, inflammatory disease that primarily attacks the spine, but can also cause pain and stiffness in other areas of the body, like your shoulder blades, hips, and feet. AS is often confused with mechanical pain—the kind caused by physical strain or injury.

Mechanical vs inflammatory back pain

It’s important to understand that AS is an inflammatory disease—not a symptom of a slipped disk, a sprain, or muscle strain.


Usually caused by physical strain to the back (eg, a sprain or muscle pull)

Typically recognized by pain that:

  • Lasts a few weeks
  • Feels better with rest
  • Can begin suddenly


Caused by the immune system attacking healthy tissue, resulting in inflammation in the joints of the spine

Typically recognized by pain that:

  • Lasts longer than 3 months
  • Feels better with exercise
  • Worsens and spreads to other areas of the body over time

Talk to your doctor if you’re experiencing any of the symptoms in the table above. Only your doctor can diagnose the type of back pain you’re suffering from.

Image of a spine showing phases of back painIf you haven’t heard of AS, you’re not alone. Part of the reason is that AS is difficult to diagnose.

Some people who have AS experience mild back pain that comes and goes, while others have chronic pain. Over time, in severe cases, the inflammation can cause the bones of the spine, neck, or rib cage to fuse together and become rigid. If bones in the rib cage fuse together, it can make breathing more difficult.

What does “ankylosing spondylitis” mean?

“Ankylosing spondylitis” comes from 2 Greek words:

  • “Ankylos” meaning stiffening of a joint
  • “Spondylo” meaning vertebrae (small bones in the backbone)

Ankylosing spondylitis (AS) is also known as Bechterew’s syndrome or Marie-Strumpell disease, and belongs to a family of disorders called spondyloarthropathies, spondyloarthritis, or spondylitis.

How common is ankylosing spondylitis?

AS affects an estimated 1 out of every 200 adults in the United States

Ankylosing spondylitis may be more common than was once thought. Studies show the prevalence of AS is an estimated 1 out of every 200 adults in the US, which comes out to about 1.1 million Americans with AS. That’s pretty close to another inflammatory joint disease—rheumatoid arthritis (RA), which affects 1.3 million people in the US.

Symptoms tend to start between 20 to 30 years of age

Unlike other forms of arthritis, AS usually affects young adults. Symptoms tend to start between 20 and 30 years of age. About 10%-20% of all people with AS start to experience symptoms before 16 years of age.

Graphic showing that ankylosing spondylitis affects close to 2 to 3 men for every woman

Experts once thought ankylosing spondylitis affected many more men than women, but new research suggests it may be closer to 2 to 3 men for every woman.

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When my rheumatologist first mentioned that I had ankylosing spondylitis, I had to ask him, ‘What is that?’

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Find out if your back or neck pain and stiffness could be ankylosing spondylitis and then talk to your doctor about your symptoms.

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AS can cause symptoms in areas besides the spine—and can get worse over time. Find out which treatment options are available and discuss with your doctor.