What Are the Symptoms of Ankylosing Spondylitis?

Back pain is no fun, and it has many different causes. Some causes — like osteoarthritis, muscle strain, and bulging discs — are more common than others. But what about when the common causes don’t apply to your back pain?

Ankylosing spondylitis (AS) is a rare type of arthritis that causes inflammation in the spine and joints, as well as other parts of the body. It affects less than 1% of adults in the U.S. Unlike other causes of back pain, it’s more common in younger people (less than 45 years of age). 

Since AS is a rare cause of back pain, it’s not typically the first thing doctors think about. However, certain symptoms provide clues that AS could be the issue.

Promotional Disclosureinfo_outlined

SPECIAL OFFER

An interchangeable biosimilar to Humira® for 92% less

Introducing Adalimumab-adbm, an autoimmune medication that is the first-ever FDA-approved interchangeable biosimilar to Humira®. Get it for 92% less than the Humira® list price.

Save now

How does ankylosing spondylitis affect your body?

AS is an autoimmune condition, meaning that the immune system (the body’s army) gets confused and causes too much inflammation. AS may affect many different parts of the body, and this is different for every person who has AS. The areas that could be involved include the:

• Spine and pelvis (most common)

• Joints and tendons

• Ribs

• Skin

• Eyes

• Bowels

• Bones

Rarely, AS can also cause inflammation in the heart, aorta (the largest blood vessel in the body), and lungs. Like many other autoimmune conditions, bodywide inflammation caused by AS also increases the risk of heart disease in general. 

What are the symptoms of ankylosing spondylitis?

The most common symptom of AS is inflammatory back pain. This is a specific type of pain that affects the back differently than other more common types of back pain. It’s usually subtle at the beginning, and then slowly worsens over the course of months to years. Pain is most common in the low back and buttocks (your sacroiliac, or SI, joints), but the mid-back and neck can be affected, too. 

Some common features of inflammatory back pain are that it: 

• Starts before age 45 

• Wakes you up in the middle of the night

• May cause a stabbing pain in the buttocks

• Is worst in the morning when you first wake up

• Is associated with significant stiffness and decreased flexibility in the spine (as if your spine needs some oil to loosen it up)

• Gets better when you’re up and moving, and then worsens with rest

• Often gets better with NSAIDs (nonsteroidal anti-inflammatory drugs) like Advil or Aleve

But it’s important to note that not all of these qualities have to be present for it to be inflammatory back pain. 

AS can also cause inflammation in areas outside of the back. For example, it can lead to:

• Inflammatory arthritis (painful, swollen joints throughout the body)

• Psoriasis (an autoimmune skin rash) 

• Inflammatory bowel disease like Crohn’s disease or ulcerative colitis (an autoimmune bowel condition)

• Iritis, also known as uveitis (inflammation inside the eye)

• Dactylitis (a condition that causes an entire finger or toe to be painful and swollen like a sausage)

• Enthesitis (pain at the back of the heel)

• Costochondritis (inflammation in the muscles between the ribs that causes pain with deep breaths in)

Last but not least, AS may cause fatigue and difficulty doing everyday activities. 

Ankylosing spondylitis symptoms in women

Both men and women with AS may develop any of the symptoms above. However, there are differences in how AS affects each sex. AS affects twice as many men as it does women. For this reason, it may take longer for women to be diagnosed with AS. Since this also delays treatment, women may have more severe symptoms at the time of diagnosis. Women are also more likely to have symptoms of AS outside of the back. 

What illnesses can mimic the symptoms of ankylosing spondylitis?

A lot of conditions can cause symptoms similar to AS. This is one of the reasons that diagnosis of AS can be difficult. Examples include:

• Fibromyalgia

• Psoriatic arthritis

• Osteoarthritis

• Diffuse idiopathic skeletal hyperostosis (DISH)

• Rheumatoid arthritis (though back pain is not a common symptom of this)

• Lower back pain in pregnancy 

What should you do if you experience AS symptoms?

The diagnosis of AS is often delayed for a number of reasons. When it is delayed, symptoms can be worse, and treatments might not work as quickly or effectively. So, if you’re worried about AS, let your healthcare provider know. That way, they can decide if a referral would be helpful to a rheumatologist (a specialist in autoimmune and joint diseases). Rheumatologists can confirm the diagnosis of AS and treat it.

Why trust our experts?

Written by:

Samantha C. Shapiro, MD

Samantha Shapiro, MD, is a board-certified rheumatologist and internist with expertise in autoimmune and inflammatory conditions. She founded the division of rheumatology at Dell Medical School at The University of Texas at Austin.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

Our editorial standards

Meet our experts