Back pain is a top medical complaint. It’s also a leading cause of missed work.

According to the National Institute of Neurological Disorders and Stroke, virtually all adults will seek attention for back pain at some point in their lives.

The American Chiropractic Association reports that Americans spend about $50 billion a year on treating back pain.

There are many possible causes of low back pain. Usually, it’s caused by trauma from a sudden strain on the spine. But you should be aware that back pain can also signal a more serious condition called ankylosing spondylitis (AS).

Unlike ordinary back pain, AS isn’t caused by physical trauma to the spine. Rather, it’s a chronic autoimmune condition caused by inflammation in the vertebrae and the bones of the spine. AS is a form of spinal arthritis.

The most common symptoms are intermittent flare-ups of spinal pain and stiffness. However, the disease can also affect other joints, as well as the eyes and the intestines.

In advanced AS, abnormal bone growth or calcification of the ligaments of the vertebral bodies of the spine may cause the joints to fuse. This can severely reduce mobility.

People with AS may also experience inflammation in other joints, such as their knees and ankles, and they may develop vision problems due to inflammation of the eyes.

Here are the warning signs of AS:

1. You have unexplained pain in the lower back

Typical back pain often feels better after rest. AS is the opposite. Pain and stiffness are usually worse upon waking.

While exercise may make ordinary back pain worse, AS symptoms may actually feel better after exercise.

Lower back pain for no apparent reason isn’t typical in young people. Teens and young adults who complain of stiffness or pain in the lower back or hips should be evaluated for AS by a doctor.

Pain is often located in the sacroiliac joints, where your pelvis and spine meet.

2. You have a family history of AS

People with certain genetic markers are susceptible to AS. But not all people with the genes develop the disease, for reasons that remain unclear.

You may have inherited genes that put you at a greater risk for AS if you have a relative with:

  • AS
  • psoriatic arthritis
  • arthritis related to inflammatory bowel disease

3. You’re young, and you have unexplained pain in the heels, joints, or chest

Instead of back pain, some AS patients first experience pain in the heel or pain and stiffness in the joints of the wrists, ankles, knees, or other joints.

Some patients’ rib bones are affected at the point where they meet the spine or where the ribs meet the sternum (breastbone). This can cause tightness in the chest, which makes it hard to breathe.

Talk with your doctor if any of these conditions occur or persist.

4. Your pain may come and go, but it’s gradually moving up your spine — and it’s getting worse

AS is a chronic, progressive disease. Although exercise or pain medications may help temporarily, the disease may gradually worsen. Symptoms may come and go, but they won’t stop completely.

Often the pain and inflammation spread from the low back up the spine. If left untreated, vertebrae may fuse together, causing a forward curvature of the spine (kyphosis).

This can be avoided if the condition is diagnosed early, and treatment is started early.

5. You get relief from your symptoms by taking NSAIDs

At first, people with AS will get symptomatic relief from common over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or naproxen.

However, these medications don’t alter the course of the disease.

If your doctors think you have AS, they may prescribe more advanced medications. These drugs target specific parts of your immune system responsible for the inflammatory response.

Immune system components called cytokines play a central role in inflammation. Two in particular — tumor necrosis factor alpha and interleukin 10 — are targeted by modern biological therapies.

These drugs may slow the progression of the disease.

Typically, the pain felt with AS is a dull, ongoing pain. Generally, you may feel some of the following:

  • stiffness and increased pain in the morning after waking up that lessens throughout the day as you move around
  • pain that worsens during sleep, which can wake you up
  • relief from light exercise, stretching, or a hot shower
  • pain may move from side to side, especially initially
  • symptoms that ease off temporarily and then return later
  • pain and inflammation in parts of the body other than the spine, such as ribs, shoulders, knees, ankles, feet, heels, Achilles tendon

In addition to pain, other AS symptoms include:

  • fatigue from your body dealing with the inflammation
  • restricted movement in the chest, which makes it hard to breathe
  • painful and red eyes
  • neurological symptoms such as pinched nerves or muscle problems
  • cardiovascular problems such as inflammation of the aorta, aortic valve disease, and ischemic heart disease

AS is more likely to affect young men, but it can affect anyone. Initial symptoms usually appear in the late teen to early adult years. AS can develop at any age, however.

The tendency to develop the disease is inherited. A genetic marker called HLA-B27 can indicate an increased risk of AS, but it isn’t always present in those with AS and doesn’t guarantee that you’ll develop it.

It’s unclear why some people get AS and others don’t.

A history of gastrointestinal or genitourinary infections may also increase the risk of developing AS, according to the National Institute for Health and Care Excellence (NICE).

There’s no single test for AS. Diagnosis involves a detailed patient history and physical exam including:

  • physical exam and questions about pain
  • mobility testing to determine flexibility and movement
  • blood tests for genetic markers such as HLA-B27
  • imaging tests, such as a CT scan, MRI scan, or X-ray

Some experts believe MRI should be used to diagnose AS in the early stages of the disease before it shows up on an X-ray.

If you find that your lower back pain (or pain in other joints) is lasting longer than you expected or you find that symptoms worsen with rest, you may want to contact your doctor for testing.

There’s currently no cure for AS, but you can reduce your symptoms and slow down the progression of the disease by:

  • finding it early
  • starting medical treatment
  • engaging in specific physical therapy and postural training exercises

Treatments are advancing, which will help you live an active and full life with AS.

Reach out to your doctor to see what could be behind your back pain.