What Are Axial Spondyloarthritis and Ankylosing Spondylitis?

Reviewed by: HU Medical Review Board | Last reviewed: September 2022

Spondyloarthritis is a type of arthritis that affects the joints and the areas where ligaments or tendons attach to bone. Axial spondyloarthritis (axSpA) is an umbrella term that refers to types of arthritis that mostly affect the spine. But axSpA can also affect other joints in the body.1

Types of axial spondyloarthritis

There are 2 types of axSpA: radiographic and non-radiographic.1

Radiographic axSpA (r-axSpA)

In radiographic axSpA, inflammation and bone damage are visible on X-rays. This is most commonly called ankylosing spondylitis (AS), which is pronounced “ankle-oh-sing spohn-dih-lie-tiss.”1

"Ankylosing" means a joint becomes stiff and difficult to move. This happens when the joints join, or fuse. “Spondylitis” means inflammation of the spine. AS causes chronic inflammation in the joints, which can lead to joint damage over time.1

Non-radiographic axSpA (nr-axSpA)

When inflammation and bone damage are not seen on an X-rays, the condition is called non-radiographic axSpA.1

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Symptoms of axial spondyloarthritis and ankylosing spondylitis

The cause of axSpA and AS symptoms is most often inflammation. It can lead to stiffness or pain, usually in the spine or back. Often, the sacroiliac (SI) joints are affected. The SI joints link your pelvis and lower spine. When these are inflamed and damaged, pelvic, hip, or lower back pain occurs.1,2

Back pain

The back and joint pain in AS and nr-axSpA are typically worse after rest and better with activity. This is the opposite of another type of arthritis called osteoarthritis. Other back pain symptom patterns may include:1,3

  • Slow onset
  • Lasts longer than 3 months
  • Improves after activity and movement
  • Waking in the middle of the night
  • Morning stiffness lasting longer than 30 minutes
  • Possible buttock pain, which can rotate sides

Changes in spinal flexibility

Problems with spinal flexibility can range from mild to total inflexibility. As the axSpA progresses, it can cause joints in the spine to fix or fuse. This can lead to a loss of mobility or a curved posture.1,3

Complete fusion of the spine is sometimes called “bamboo spine” because of its appearance on X-ray.1,3

Changes in bone formation

Changes in bone formation cause spinal deformities. They also can cause the shoulders or hips to not work properly. Some people have pain and inflammation in other joints from these changes, too, like the shoulders, ribs, hands, or feet.1,3

Other symptoms

About 4 in 10 people with AS also experience inflammation in their eyes. This is called uveitis or iritis. It can cause eye pain and sensitivity to light (photophobia). Uveitis requires treatment to decrease inflammation and help prevent vision loss.4,5

Other symptoms of axSpA may include:1,3

  • Heel or foot pain
  • Anxiety or depression
  • Fatigue
  • Pain in other joints
  • “Sausage-like” swelling of the fingers or toes (dactylitis)

Who gets axial spondyloarthritis and ankylosing spondylitis?

The exact number of people with axSpA is not well known. It usually begins between the ages of 20 and 40. But the condition can occur at any age.1

In the past, doctors thought that axSpA occurred much more often in men than in women. While men are diagnosed with axSpA more often than women, doctors now think the disease may occur at the same rate in all genders. This is because the condition looks different in women than it does in men.6

AS occurs more frequently in white adults than in Black adults. But Black adults tend to have more severe disease and greater levels of impairment.7

What causes axial spondyloarthritis and ankylosing spondylitis?

The exact cause is not known. Doctors think a combination of genes and environment leads to symptoms.1

Several gene changes (genetic mutations) have been linked to AS. The most common is on the HLA-B27 gene. But not everyone who has one of these mutations will develop AS. Also, many people with AS do not have any of the known genetic mutations.1,3

How are they diagnosed?

Usually, a doctor called a rheumatologist makes the diagnosis. Diagnosing axSpA involves a combination of tests and exams, including:1,3

  • Physical exam
  • Medical history
  • Family history
  • X-rays
  • Magnetic resonance imaging (MRI)
  • Blood work

How are they treated?

There is currently no cure for axSpA. Treatment usually involves a combination of drugs, physical therapy, and exercise. In some cases, surgery may be recommended to relieve severe joint damage.1,3

Many people with axSpA also find complementary methods helpful in relieving symptoms, such as using heat and cold or making dietary changes.1,3

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