Back pain is one of the most common ailments in the United States today. Roughly 80 percent of adults experience back pain at some point in life.

Many of these cases are caused by injury or damage. However, some may be the result of another condition. One is a form of arthritis called ankylosing spondylitis (AS).

AS is a progressive inflammatory condition that causes inflammation in your spine and nearby joints in the pelvis. Over a long-period of time, the chronic inflammation can cause the vertebrae in your spine to fuse together, making your spine less flexible.

People with AS can hunch forward because the extensor muscles are weaker than the flexor muscles that pull the body forward (flexion).

As the spine becomes stiffer and fuses, the hunching becomes more pronounced. In advanced cases, a person with AS can’t lift their head in order to see in front of them.

While AS mainly affects the spine and vertebrae where tendons and ligaments connect to the bone, it can also affect other joints, including the shoulders, feet, knees, and hips. In rare cases, it can also affect organs and tissue.

Compared to other forms of arthritis, one unique characteristic of AS is sacroiliitis. This is inflammation of the sacroiliac joint, where the spine and pelvis connect.

Men are affected by AS more often than women, though it may be less recognized in women.

For the millions of Americans with chronic back pain, understanding this condition may be key to managing pain and possibly diagnosing inflammatory back pain like AS.

Doctors don’t have a single test to diagnose AS, so they must rule out other possible explanations for your symptoms, and look for the characteristic cluster of signs and symptoms of AS. To do this, your doctor conducts a physical exam and other tests.

Your doctor will also want to get your full health history in order to better understand your symptoms. Your doctor will also ask you:

  • how long you’ve been experiencing symptoms
  • when your symptoms are worse
  • what treatments you’ve tried, what has worked, and what hasn’t
  • what other symptoms you’re experiencing
  • your history of medical procedures or problems
  • any family history of problems similar to what you’re experiencing

Let’s take a look at what you can expect of the tests your doctor may perform to diagnose AS.

A full physical exam

Your doctor conducts a physical exam in order to find telltale signs and symptoms of AS.

They may also passively move your joints or have you do a few exercises so they can observe the range of motion in your joints.

Imaging tests

Imaging tests give your doctor an idea of what’s happening inside your body. The imaging tests you need may include:

  • X-ray: An X-ray allows your doctor to see your joints and bones. They will look for signs of inflammation, damage, or fusion.
  • MRI scan: An MRI sends radio waves and a magnetic field through your body to produce an image of your body’s soft tissues. This helps your doctor see inflammation within and around joints.

Laboratory tests

Lab tests your doctor may order include:

  • HLA-B27 gene test: Decades of research into AS have revealed one detectable risk factor: your genes. People with the HLA-B27 gene are more susceptible to developing AS. However, not everyone with the gene will develop the disease.
  • Complete blood count (CBC): This test measures the number of red and white blood cells in your body. A CBC test can help identify and rule out other possible conditions.
  • Erythrocyte sedimentation rate (ESR): An ESR test uses a blood sample to measure inflammation in your body.
  • C-reactive protein (CRP): The CRP test also measures inflammation, but is more sensitive than an ESR test.

You may first discuss your back pain with your primary care doctor.

If your primary doctor suspects AS, they may refer you to a rheumatologist. This is a type of doctor specializing in arthritis and other conditions that affect the muscles, bones, and joints, including a range of autoimmune diseases.

The rheumatologist is generally the one to accurately diagnose and treat AS.

Because AS is a chronic condition, you may work with your rheumatologist for years. You’ll want to find one you trust and who has experience with AS.

Doctor appointments can sometimes feel rushed and stressful. It’s easy to forget to ask a question or mention a detail about your symptoms.

Here are something things to do ahead of time that can help you get the most out of your appointment:

  • Make a list of questions you want to ask the doctor.
  • Write out a timeline of your symptoms, including when they started and how they progressed.
  • Gather test results or medical records to show the doctor.
  • Write down anything about your family’s medical history that you think could help the doctor with diagnosis or treatment.

Being prepared will help you make the best use of your time when you see your doctor. Bringing notes can also help relieve the pressure of feeling like you need to remember everything.