Ankylosing Spondylitis (AS)

What Is Ankylosing Spondylitis?

Ankylosing spondylitis is a form of progressive arthritis due to chronic inflammation of the joints in the spine. Its name comes from the Greek words “ankylos,” meaning stiffening of a joint, and “spondylo,” meaning vertebra. Spondylitis refers to inflammation of the spine or one or more of the adjacent structures of the vertebrae.

Ankylosing spondylitis belongs to a group of disorders called seronegative spondyloarthropathies. Seronegative means an individual has tested negative for an autoantibody called rheumatoid factor. The spondyloarthropathies are a family of similar diseases that usually cause joint and spine inflammation. Other well-established syndromes in this group include psoriatic arthritis, the arthritis of inflammatory bowel disease, chronic reactive arthritis, and enthesitis-related idiopathic juvenile arthritis.

Although these disorders have similarities, they also have features that distinguish them from one another. The hallmark of ankylosing spondylitis is “sacroiliitis,” or inflammation of the sacroiliac (SI) joints, where the spine joins the pelvis.

In some people, ankylosing spondylitis can affect joints outside of the spine, like the shoulders, ribs, hips, knees, and feet. It can also affect entheses, which are sites where the tendons and ligaments attach to the bones. It is possible that it can affect other organs, such as the eyes, bowel, and—more rarely—the heart and lungs.

Although many people with ankylosing spondylitis have mild episodes of back pain that come and go, others have severe, ongoing pain accompanied by loss of flexibility of the spine. In the most severe cases, long-term inflammation leads to calcification that causes two or more bones of the spine to fuse. Fusion can also stiffen the rib cage, resulting in restricted lung capacity and function.

Who Has Ankylosing Spondylitis?

Ankylosing spondylitis typically begins in adolescents and young adults, but it affects people for the rest of their lives. Men are more likely to develop ankylosing spondylitis than are women.

What Causes Ankylosing Spondylitis?

The cause of ankylosing spondylitis is unknown, but it is likely that both genes and factors in the environment play a role. The main gene associated with susceptibility to ankylosing spondylitis is called HLA-B27. But while most people with ankylosing spondylitis have this genetic marker, only a small percentage of people with the gene develop the disease.

How Is Ankylosing Spondylitis Diagnosed?

A diagnosis of ankylosing spondylitis is based largely on the findings of a medical history and physical exam. Radiologic tests and lab tests may be used to help confirm a diagnosis, but both have some limitations.

Medical History

The medical history involves answering questions, such as the following:

  • How long have you had pain?
  • Where specifically is the pain in your back or neck? Are other joints affected?
  • Is back pain better with exercise and worse after inactivity, such as when you first get up in the morning?
  • Do you have other problems, such as eye problems or fatigue?
  • Does anyone in your family have back problems or arthritis?
  • Have you recently suffered from a gastrointestinal illness?
  • Do you have any skin rashes such as psoriasis?

From your answers to these questions, your doctor can begin to get an idea of the diagnosis.

Physical Exam

During the physical exam, the doctor will look for signs and symptoms that are consistent with ankylosing spondylitis. These include pain along the spine and/or in the pelvis, sacroiliac joints, heels, and chest. Your doctor may ask you to move and bend in different directions to check the flexibility of your spine and to breathe deeply to check for any problems with chest expansion, which could be caused by inflammation in the joints where the ribs attach to the spine.

Radiologic Tests

X rays and magnetic resonance imaging (MRI) may be used in making or confirming a diagnosis of ankylosing spondylitis, but these tests have limitations. X rays may show changes in the spine and sacroiliac joints that indicate ankylosing spondylitis; however, it may take years of inflammation to cause damage that is visible on x rays. MRI may allow for earlier diagnosis, because it can show damage to soft tissues and bone before it can be seen on an x ray. Both tests may also be used to monitor the progression of ankylosing spondylitis.

Lab Tests

The main blood test for ankylosing spondylitis is one to check for the HLA-B27 gene, which is present in the majority of Caucasians with ankylosing spondylitis. However, this test also has limitations. The gene is found in much lower percentages of African Americans with ankylosing spondylitis, and in ankylosing spondylitis patients from some Mediterranean countries. Also, the gene is found in many people who do not have ankylosing spondylitis, and will never get it. Still, when the gene is found in people who have symptoms of ankylosing spondylitis and/or x-ray evidence of ankylosing spondylitis, this finding helps support the ankylosing spondylitis diagnosis.

What Type of Doctor Diagnoses and Treats Ankylosing Spondylitis?

The diagnosis of ankylosing spondylitis is often made by a rheumatologist, a doctor specially trained to diagnose and treat arthritis and related conditions of the musculoskeletal system. However, because ankylosing spondylitis can affect different parts of the body, a person with the disorder may need to see several different types of doctors for treatment. In addition to a rheumatologist, there are many different specialists who treat ankylosing spondylitis. These may include:

  • An ophthalmologist, who treats eye disease.
  • A gastroenterologist, who treats bowel disease.
  • A physiatrist, a medical doctor who specializes in physical medicine and rehabilitation.
  • A physical therapist or rehabilitation specialist, who supervises stretching and exercise regimens.

Often, it is helpful to the doctors and the patient for one doctor to manage the complete treatment plan.

Can Ankylosing Spondylitis Be Cured?

There is no cure for ankylosing spondylitis, but some treatments relieve symptoms of the disorder and may possibly prevent its progression. In most cases, treatment involves a combination of medication, exercise, and self-help measures. In some cases, surgery may be used to repair some of the joint damage caused by the disease.

What Medications Are Used to Treat Ankylosing Spondylitis?

Several classes of medications are used to treat ankylosing spondylitis. Because there are many medication options, it’s important to work with your doctor to find the safest and most effective treatment plan for you. A treatment plan for ankylosing spondylitis will likely include one or more of the following:1

Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)

These drugs relieve pain and inflammation, and are commonly used to treat ankylosing spondylitis. Aspirin, ibuprofen, and naproxen are examples of NSAIDs. All NSAIDs work similarly by blocking substances called prostaglandins that contribute to inflammation and pain. However, each NSAID is a different chemical, and each has a slightly different effect on the body.


Some NSAIDs are available over the counter, but more than a dozen others, including a subclass called COX-2 inhibitors, are available only with a prescription.

All NSAIDs can have significant side effects, and for unknown reasons, some people seem to respond better to one NSAID than another. Anyone taking NSAIDs regularly should be monitored by a doctor.

Corticosteroids

These strong inflammation-fighting drugs are similar to the cortisone made by our bodies. If NSAIDs alone do not control inflammation in people with ankylosing spondylitis, doctors may inject corticosteroids directly into the affected joints to bring quick but temporary relief. Injections may be given to the sacroiliac joint, hip joint, or knee joint, but are not given in the spine.

Disease-Modifying Antirheumatic Drugs (DMARDs)

These drugs work in different ways to control the disease process of ankylosing spondylitis. The most commonly used DMARDs for ankylosing spondylitis are sulfasalazine and methotrexate.

Biologic Agents

Members of this class of medications are genetically engineered to block proteins involved in the body’s inflammatory response. Five biologics—adalimumab, certolizumab, etanercept, golimumab, and infliximab—are approved by the Food and Drug Administration (FDA) for treating ankylosing spondylitis. All four work by suppressing a protein called tumor necrosis factor-alpha (TNF-α), and are often effective for relieving symptoms when NSAIDs or other treatments are not. These drugs are taken by intravenous infusion or injection.

Will Diet and Exercise Help?

A healthy diet and exercise are good for everyone, but may be especially helpful if you have ankylosing spondylitis.

Exercise and stretching, when done carefully and increased gradually, may help painful, stiff joints.

  • Strengthening exercises, performed with weights or done by tightening muscles without moving the joints, build the muscles around painful joints to better support them. Exercises that don’t require joint movement can be done even when your joints are painful and inflamed.
  • Range-of-motion exercises improve movement and flexibility and reduce stiffness in the affected joint. If the spine is painful and/or inflamed, exercises to stretch and extend the back can be helpful in preventing long-term disability.

Many people with ankylosing spondylitis find it helpful to exercise in water.

Before beginning an exercise program, it’s important to speak with a health professional who can recommend appropriate exercises.

When Might Surgery Be Necessary, and How Can It Help?

If ankylosing spondylitis causes severe joint damage that makes it difficult to do your daily activities, total joint replacement may be an option. This involves removing the damaged joint and replacing it with a prosthesis made of metals, plastics, and/or ceramic materials. The most commonly replaced joints are the knee and hip.

In very rare cases, a procedure called osteotomy may be used to straighten a spine that has fused into a curved-forward position. This surgery involves cutting through the spine so that it can be realigned to a more vertical position. After the bones are realigned, hardware may be implanted to hold them in their new position while the spine heals.

Surgery to straighten the spine can only be done by a surgeon with significant experience in the procedure. Many doctors and surgeons consider the procedure high risk.

What Are Some Things I Can Do to Help Myself?

Aside from seeing your doctor regularly and following your prescribed treatment plan, staying active is probably the best thing you can do for ankylosing spondylitis. Regular exercise can help relieve pain, improve posture, and maintain flexibility. Before beginning an exercise program, speak with your doctor or physical therapist about designing a program that’s right for you.

Another important thing you can do for yourself is to practice good posture. A good test for posture is to check yourself in a mirror. First, stand with a full-length mirror to your side and, if possible, turn your head to look at your profile. Next, imagine you have dropped a weighted string from the top of your head to the soles of your feet. Where does the string fall? If your posture is good, it should pass through your earlobe, the front of your shoulder, the center of your hip, behind your kneecap, and in front of your anklebone. If you are not standing that way already, practice holding your body that way in front of a mirror until you know well how it feels. Practicing good posture can help you avoid some of the complications that can occur with ankylosing spondylitis.

What Is the Prognosis for People With Ankylosing Spondylitis?

The course of ankylosing spondylitis varies from person to person. Some people will have only mild episodes of back pain that come and go, while others will have chronic severe back pain. In almost all cases, the condition is characterized by acute, painful episodes and remissions, or periods of time where the pain lessens.

In the sacroiliac joints and spine, inflammation can cause pain and stiffness. Over time, bony outgrowths called syndesmophytes can develop that cause the vertebrae to grow together, or fuse. Fusion can also stiffen the rib cage, resulting in restricted lung capacity and restricted lung function.

A number of factors are associated with an ankylosing spondylitis prognosis. One study found that among people who had ankylosing spondylitis for at least 20 years, those who had physically demanding jobs, other health problems, or smoked had greater functional limitations from their disease. People with higher levels of education and a history of ankylosing spondylitis in the family tended to have less severe limitations from their disease.

A study supported by the NIAMS found that the likelihood of having severe joint damage increased with age at disease onset, and that men were twice as likely as women to be in that group. The study also found that current smokers were more than four times as likely to have severe damage as nonsmokers, and that having a genetic marker called DRB1*0801 seemed to protect against severe spine damage.


Reference: National Institutes of Health

Last Updated January 7, 2017

1 All medicines can have side effects. Some medicines and side effects are mentioned in this publication. Some side effects may be more severe than others. You should review the package insert that comes with your medicine and ask your health care provider or pharmacist if you have any questions about the possible side effects.

2 Warning: Side effects of NSAIDs include stomach problems; skin rashes; high blood pressure; fluid retention; and liver, kidney, and heart problems. The longer a person uses NSAIDs, the more likely he or she is to have side effects, ranging from mild to serious. Many other drugs cannot be taken when a patient is being treated with NSAIDs, because NSAIDs alter the way the body uses or eliminates these other drugs. Check with your health care provider or pharmacist before you take NSAIDs. NSAIDs should only be used at the lowest dose possible for the shortest time needed.

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