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And it could be what’s causing your unexplained back pain.

There’s a good chance you’ve probably never heard of axial spondyloarthritis (axSpA), commonly known as inflammatory arthritis of the spine. And that’s okay—most people haven’t. But just because you’re unfamiliar with the name doesn’t make living with axSpA any less painful, or even make the journey to relief any less real. These conditions are beasts that, once caught, can be tamed.


AxSpA is an inflammatory arthritis of the spine that is made up of two underdiagnosed conditions: non-radiographic axial spondyloarthritis (nr-axSpA) and ankylosing spondylitis (AS). What causes the inflammation is unknown, but when inflammation occurs within the spinal joints and vertebrae, it causes chronic lower back pain, stiffness, fatigue, and reduced mobility. If left untreated, axSpA can cause irreversible damage, and in some cases, fusion of spinal joints and vertebrae.

It’s important to know that axSpA also affects men and women differently. AS is more likely to affect men, whereas nr-axSpA is more likely to affect women. Men with AS are more likely to experience symptoms in the back and spine, whereas women with AS are more likely to experience pain in the hips, neck, and knees. But that doesn’t mean men won’t develop nr-axSpA and women won’t develop AS. They do. And living with it can be a monster pain.

Two forms of axSpA: non-radiographic axial spondyloarthritis (nr-axSpA) and ankylosing spondylitis (AS)



AxSpA is a type of inflammatory arthritis of the spine that can often cause stiffness, fatigue, and reduced mobility. While these symptoms may first appear in the lower back, they often affect other parts of the body, including the hips, shoulders, knees, heels, buttocks, and thighs. But as the disease progresses, pain and stiffness may even reach the neck.


  • zzz

    Fatigue and trouble sleeping

  • sun in moon

    Pain, stiffness, and reduced mobility in the lower back that worsens in the morning or at night

  • pain

    Pain that affects other areas of the body, including the hips, shoulders, knees, heels, buttocks, thighs, and neck

  • fire


AXSPA Diagnosis


AxSpA is difficult to diagnose, and many people live with it for years before they’re officially diagnosed by a rheumatologist. A rheumatologist will typically look at how inflammation is not only affecting the parts of the body that are in pain, but also at how that inflammation is affecting the entire body. To make a diagnosis, a rheumatologist will look at a patient's history and may perform a variety of tests including physical exams, imaging, and lab tests.

Find a rheumatologist.


Physical Exams


A rheumatologist will check for signs of inflammation, pain, and tenderness throughout the body, and may test your range of motion by asking you to perform certain movements or physical tasks.

If any close relatives have been diagnosed with spondyloarthritis, AS, nr-axSpA, psoriatic arthritis, acute anterior uveitis, reactive arthritis, inflammatory bowel disease, or psoriasis, tell your doctor. A family history of other autoimmune conditions may provide clues for your doctor. Download this Family Conversation Starter.

Imaging Tests


X-rays, MRIs, CT scans, and ultrasounds can all reveal signs of joint damage or inflammation inside the body that may indicate axial spondyloarthritis. However, nr-axSpA may not appear on an X-ray.

Lab Tests


Although its exact cause is unknown, a specific protein called HLA-B27 is thought to play an important part in axSpA. But it is possible to have axSpA and not test positive for the HLA-B27 protein. Blood tests can determine if you’re a carrier of the HLA-B27 protein, or they can be used to check your C-reactive protein (CRP) levels.

A C-reactive protein test measures the level of CRP in your blood. High levels of CRP may be a sign of inflammation or other disorders. These tests can also rule out other conditions or diseases.

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Both conditions have similar symptoms of back pain, fatigue, and reduced activity. The main difference is that spinal fusion or damage from ankylosing spondylitis (AS) will appear on an X-ray, while with non-radiographic axial spondyloarthritis (nr-axSpA), no definitive damage will appear.

Can you say that for me?

Their names are a mouthful, and their acronyms can be even more confusing. Don’t you want to know what these words even mean? Let's break it down.


may not appear on imaging techniques, like X-rays

ax·i·al (ax-eel)
spon·dy·lo·ar·thri·tis (spon-dill-lo-ar-thri-tiss)

a type of arthritis that attacks the spine

an·ky·lo·sing (an-kih-low-sing)

the abnormal stiffening and immobility of a joint due to fusion of the bones

spon·dyl·i·tis (spon-dill-eye-tiss)

the inflammation of the spine, or vertebrae

Non-radiographic Axial Spondyloarthritis (nr-axSpA)

  • does not show on xray

    Damage may not appear on X-ray, but may appear on an MRI

  • female

    nr-axSpA patients are more likely to be female (50–60%)

  • joint

    nr-axSpA may be considered an early form of AS in some patients

Ankylosing Spondylitis (AS)

  • joint pain

    Joint damage and spinal fusion

  • shows on xray

    Damage will appear on X-rays

  • male

    AS patients are more likely to be male

At one time, it was believed that men were more likely than women to develop AS and nr-axSpA. But because symptoms may be different and not commonly looked for in women, the ratio of men to women may not be as high as once thought.

Even though damage caused by nr-axSpA may not appear on an X-ray, people with this condition are still at risk of long-term damage. In fact, up to 50% of nr-axSpA cases are at risk of progressing to AS, which may cause irreversible spinal fusion.


It’s not uncommon for axSpA to be misdiagnosed or mistaken for other conditions. Many people with axSpA are thought to have rheumatoid arthritis (RA) or fibromyalgia. One reason for this is that the symptoms of axSpA are so similar to those of many other conditions.

AXSPA versus RA and fibromyalgia

Axial Spondyloarthritis

  • 1.7

    AxSpA and related conditions affect approximately 1.7 million people in the United States

  • <45
    (often in the mid-20s)

    Usual age of onset

  • Primarily affects joints in the spine and lower back, but can also affect the neck, hips, shoulders, thighs, and heels

Rheumatoid Arthritis

  • 1.5

    Affects approximately 1.5 million people in the United States

  • 30-60

    Usual age of onset

  • Primarily affects joints in the arms, hands, legs, and feet


  • 4

    Affects approximately 4 million people in the United States

  • 20-50

    Usual age of onset

  • Can affect many different areas of the body

Find a Rheumatologist. BOOK AN APPOINTMENT NOW.

A rheumatologist will understand the types of tests needed to properly diagnose nr‑axSpA and AS. Your quiz results, and knowledge of your family history, could help your rheumatologist discover what’s causing your pain. Download this Family Conversation Starter, and find a local rheumatologist who may help.