Orthopedist examining patient's back

What is ankylosing spondylitis?

Ankylosing spondylitis (AS), also known as axial spondyloarthritis, is a chronic inflammatory condition that primarily affects the spine. Over time, inflammation can lead to the fusion of some vertebrae, which are the bones that make up your spine. This fusion can cause stiffness and reduce flexibility, leading to discomfort.

AS typically starts at the sacroiliac joints, where the base of your spine (the sacrum) connects with your pelvis (the ilium). These joints are some of the largest in the body and are essential for movement, especially when shifting or rotating your hips. The inflammation in these joints is often one of the earliest signs of the condition.

While the sacroiliac joints are most affected, ankylosing spondylitis can also impact other areas of the body. Less frequently, AS affects other joints, including:

  • Shoulders
  • Hips
  • Knees

While there is no cure for ankylosing spondylitis, early diagnosis and treatment can help manage the symptoms, slow the progression of the condition and improve the quality of your life.

Ankylosing spondylitis symptoms

Everyone with ankylosing spondylitis experiences different symptoms. The most common symptom is lower back pain caused by sacroiliitis, which is painful inflammation in the sacroiliac joints.

The pain can spread to other areas, including:

  • Hip pain
  • Pain in your buttocks
  • Neck pain
  • Abdominal pain

Other symptoms of AS may include:

  • Stiffness or difficulty moving your hips and lower back, especially in the morning or after resting for a long time
  • Fatigue
  • Shortness of breath
  • Loss of appetite or unexplained weight loss
  • Diarrhea
  • Skin rashes
  • Vision problems

When to see a doctor

See a doctor if you have persistent lower back pain, stiffness or discomfort that spreads to your hips, buttocks or neck. Also, get medical advice if you're feeling constantly fatigued, losing weight without explanation or having digestive issues like diarrhea. Early diagnosis and treatment can help manage symptoms and prevent complications.

Ankylosing spondylitis causes

Ankylosing spondylitis is an autoimmune condition. This means your immune system mistakenly attacks your body instead of protecting it.

The exact cause of ankylosing spondylitis isn’t fully understood. However, studies show that certain genetic mutations are strongly linked to the condition. Genetic mutations are changes in your DNA that occur when your cells make copies of themselves.

More than 60 genes may be linked to AS. One example is the human leukocyte antigen-B (HLA-B27) gene. Having a gene known as HLA-B27 increases your risk, but not everyone with this gene develops the condition, which means environmental factors could also play a part. 

Ankylosing spondylitis risk factors

While researchers aren’t exactly sure what causes ankylosing spondylitis, certain risk factors can make it more likely to develop. These include:

  • Age: Symptoms usually start between the ages of 18 and 40.
  • Family history: If you have family members with ankylosing spondylitis, you may be at a higher risk.
  • Sex: Ankylosing spondylitis is more common in men than women.
  • Certain conditions: If you have conditions like Crohn’s disease, ulcerative colitis or psoriasis, you may be more likely to develop ankylosing spondylitis.

Complications of ankylosing spondylitis

In severe cases of ankylosing spondylitis, the body forms new bone as it tries to heal itself. Over time, this new bone can connect the vertebrae in the spine, causing sections of the spine to fuse. This makes the spine stiff and less flexible. The fusion can also affect the rib cage, limiting how much your lungs can expand.

Other possible complications include:

  • Eye inflammation (uveitis): This is a common issue with ankylosing spondylitis and can cause sudden eye pain, sensitivity to light and blurry vision.
  • Fractures: Early in the disease, bones can weaken, especially in the spine. This can cause vertebrae to collapse, which can lead to a stooped posture. These fractures may also put pressure on the spinal cord or nerves, which can cause further damage.
  • Neurological impairment: In the later stages of the condition, when the bones in the spine have fused together, a break in the spine can be very serious. It can snap straight across and damage the nerves, leading to neurological problems like weakness or paralysis.
  • Heart problems: Ankylosing spondylitis can affect the aorta, the large artery in your body. Inflammation can make the aorta enlarge, which can affect how the aortic valve works. This can increase the risk of heart disease as well.

How is ankylosing spondylitis diagnosed?

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Diagnosing ankylosing spondylitis can be difficult. Many of its symptoms are similar to those of other conditions and no definitive test exists for it. Your doctor will do a physical exam and talk to you about your personal and family health history. Imaging tests and blood work can also help your doctor determine the cause of your symptoms and make an accurate diagnosis.

Medical history and exam

Your doctor will review your medical history and ask about your symptoms. They’ll want to know where you feel discomfort, how long it’s been happening and what makes it worse. Your doctor will also ask if anyone in your family has had arthritis or back pain.

During the physical exam, your doctor will focus on your spine and other joints that may be affected, such as your pelvis, chest and heels. You may be asked to bend in different directions and take deep breaths to check for stiffness in your ribs.

Lab tests

There are no specific lab tests to diagnose ankylosing spondylitis. However, certain blood tests can check for signs of inflammation, though many other health conditions can cause inflammation as well.

Blood tests may also check for the HLA-B27 gene. While many people with this gene do not have ankylosing spondylitis and some people with the condition may not have the gene, it can still provide useful information.

Imaging tests

Imaging tests can help your doctor look for signs of ankylosing spondylitis and identify any inflammation or genetic markers that might suggest the condition.

Based on the results of your physical exam, your doctor may recommend:

  • X-rays: Joint changes that signal ankylosing spondylitis may not show up on X-rays until the condition has advanced. However, your doctor may use X-rays to rule out other causes of joint pain and monitor your condition over time.
  • Magnetic resonance imaging (MRI) scan: An MRI creates images using radio waves and a powerful magnet. These images allow your doctor to see your joints and can help diagnose ankylosing spondylitis in its early stages.
  • Computed tomography (CT) scan: A CT scan provides more detailed images than an X-ray and is particularly useful for evaluating fractures and assessing the extent of bony changes in advanced stages of ankylosing spondylitis.

Ankylosing spondylitis treatment

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Ankylosing spondylitis treatment focuses on managing discomfort, reducing inflammation and helping you keep your mobility and posture. While there’s no cure, effective treatments can make a big difference in your quality of life by controlling symptoms and slowing the condition's progression. Treatment usually includes medications, physical therapy, exercise, and in some cases, surgery.

Physical therapy

Your doctor may suggest physical therapy to help you stay active and follow an exercise program that works for you. Physical therapy can help reduce pain, strengthen muscles (especially those that support your back), improve posture and increase joint flexibility. A physical therapist can also show you sleeping positions that might reduce discomfort from ankylosing spondylitis at night.

The goal of physical therapy is not only to relieve pain but also to help you keep an active lifestyle and prevent further joint damage. It can also teach you how to manage your symptoms in the long run, which is important since ankylosing spondylitis is a chronic condition.

Medication

There are several medications to help manage symptoms of ankylosing spondylitis:

  • Over-the-counter pain relievers: Medications like acetaminophen or NSAIDs (ibuprofen, aspirin, naproxen) can reduce pain and inflammation.
  • Corticosteroids: If your symptoms are severe, your doctor may recommend corticosteroid injections to reduce inflammation and relieve joint pain.
  • Anti-tumor necrosis factor (TNF) medications: These medications block TNF, a protein that causes inflammation. Anti-TNF medications can reduce inflammation and may help slow down the progression of ankylosing spondylitis. They are often recommended if other medications aren’t effective.
  • Janus kinase (JAK) inhibitors: These newer medications target inflammation at the cellular level and may be used if other treatments don’t work. They’re usually taken as oral tablets.

Your doctor will help you find the right medication based on your symptoms and how well you respond to other treatments.

Surgery

Surgery is usually not needed for ankylosing spondylitis. However, in some cases, surgery may be recommended if other treatments don’t relieve pain or if joint damage becomes severe:

  • Joint repair or replacement: If ankylosing spondylitis causes serious damage to joints, especially the hips or knees, your doctor may recommend surgery to repair or replace the damaged joint.
  • Spinal surgery: In some cases, the condition can cause spinal fractures or deformities. If this leads to severe pain or difficulty moving, surgery may be necessary to fix spinal fractures or straighten the spine.

Frequently asked questions

  • Is ankylosing spondylitis an autoimmune disease?

    Yes, ankylosing spondylitis is an autoimmune disease. This means your immune system mistakenly attacks your spine’s joints, causing pain and swelling. Over time, the inflammation can make the vertebrae fuse together, leading to stiffness and less flexibility.

  • Is ankylosing spondylitis genetic?

    Yes, ankylosing spondylitis has a strong genetic link, particularly with the HLA-B27 gene. While genetics play a significant role, environmental factors also contribute. Not everyone with the HLA-B27 gene will develop AS and family history increases the risk but other factors are involved in the condition's development.

  • Can ankylosing spondylitis be cured?

    Ankylosing spondylitis can’t be cured, but treatments can help manage pain, stiffness and movement problems. Medications, physical therapy and lifestyle changes can make a big difference in controlling symptoms and slowing the condition, helping you live a better quality of life.

  • Can ankylosing spondylitis cause headaches?

    Yes, ankylosing spondylitis can cause headaches, even though they aren't a primary symptom of the condition. AS mainly affects the spine and sacroiliac joints, but it can also impact the cervical spine (neck). When the neck becomes stiff and painful, it can lead to tension that radiates to the head and cause headaches.

  • How common is ankylosing spondylitis?

    Ankylosing spondylitis affects about 1 in 1,000 people in the US. It occurs more frequently among Caucasian people and in men. AS is part of a larger group of conditions called spondyloarthritis, which is more common than rheumatoid arthritis, multiple sclerosis and ALS combined.

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