Ankylosing spondylitis

Marie-Strumpell Arthritis

What is Ankylosing spondylitis?

Ankylosing spondylitis (AS) is type of chronic arthritis that primarily affects the spine. The joints between the vertebrae of the spine and ligaments that allow the back to move become inflamed, sometimes leading to the joints and bones fusing together. This inflammation often leads to stiffness of the back and hips.

The name of the disease describes its destructive nature. “Ankylosing” means stiff or rigid, "spondyl" refers to the spine, and "itis" means inflammation. AS belongs to a family of diseases known as spondylarthropathies that attack the spine. These diseases include psoriatic arthritis, Reiter's syndrome (a form of reactive arthritis, sparked by infection) and enteropathic arthritis (arthritis related to digestive disorders such as inflammatory bowel disease or celiac disease).

While AS progresses, it can also cause inflammation of other organs in the body, including the eyes, lungs and heart valves. Anemia (reduced number of red blood cells) is also associated with the chronic inflammation of ankylosing spondylitis.

The impact of AS varies widely from individual to individual. Some patients experience episodes of back pain that come and go, whereas others have chronic symptoms that worsen and cause severe joint and back stiffness, loss of motion and deformity.

Risk factors and potential causes of AS

The exact cause of ankylosing spondylitis (AS) remains unknown. However, genetics may be a factor, because a gene called HLA-B27 occurs in more than 90 percent of patients with the disease, according to the Arthritis Foundation. However, not everybody with HLA-B27 develops ankylosing spondylitis. People with HLA-B27 who have no relative with AS have only a 2 percent chance of developing the disease, whereas people with the gene who do have a parent or sibling with AS have a 20 percent chance of developing AS.

In 2007 two other gene variants were linked to AS: IL23R and ARTS1. People who have both of these and HLA-B27 may have a 25 percent chance of developing AS.

AS is believed to be an autoimmune disease, meaning that the patient's immune system is hyperactive and mistakenly attacks the body's own tissues. Other examples of autoimmune diseases include rheumatoid arthritis, psoriatic arthritis and inflammatory bowel disease.

AS primarily affects boys and men between the ages of 16 and 35. It is less common in women, although it may develop during pregnancy. It is also normally less severe in women, making it harder to diagnose. AS is more common in American Indians than in other racial and ethnic groups, according to the American College of Rheumatology.

About 5 percent of cases develop in children. AS is more likely to appear in boys than girls. Symptoms in children usually begin in the hips, knees, heels or big toes before progressing to the spine.

Signs and symptoms of ankylosing spondylitis

The most common symptom of ankylosing spondylitis (AS) is low back pain and stiffness due to inflammation. This usually begins around the sacroiliac joints, where the lower spine joins the pelvis. It may take days or weeks to develop.

Inactivity tends to make symptoms worse, and many patients experience back pain in the middle of the night and may feel stiff in the morning. Movement and exercise tend to reduce symptoms.

As the disease progresses, it may cause inflammation in the upper spine, chest and neck. As the inflammation associated with AS persists, new bone forms during the healing process, causing the vertebrae to grow together. This results in the formation of bony outgrowths (syndesmophytes) that cause the spine to become stiff and inflexible. This process can also occur in the rib cage, restricting lung capacity and function.

Other joints that may become inflamed include the hips, shoulder, knees or ankles. In some cases, the heels are affected and the patient may find it uncomfortable to stand or walk on hard surfaces. In other cases, inflammation can reach the heart, increasing the risk of heart problems. The severity of symptoms and level of disability triggered by AS vary from person to person.

Symptoms associated with more advanced cases of AS include:

  • Restricted expansion of the chest and chest pain
  • Chronic stooping
  • Stiff, inflexible spine
  • Loss of lateral flexion (bending sideways)
  • Tenderness over the sacroiliac joint
  • Fatigue
  • Loss of appetite
  • Unexplained weight loss
  • Bowel inflammation
  • Inflammation of the iris (iritis) and eye pain

Patients may have other symptoms if the heart or lungs are involved.

eye anatomy

How is ankylosing spondylitis diagnosed?

In diagnosing ankylosing spondylitis (AS), a physician is likely to begin by reviewing the patient's medical history and performing a physical examination. X-rays may be taken to see whether or not the sacroiliac joint is inflamed. In severe and longstanding cases of AS, calcification of ligaments in the back occurs. On x-rays, this gives the back a "bamboo-spine" appearance. In some other cases, a bone scan or CAT scan (computed axial tomography) is used to view these internal features.

The physician may take a blood sample to check for the presence of genes such as HLA-B27, which is present in about 90 percent of patients with ankylosing spondylitis. Blood tests may also be used to check for elevated sedimentation rate - a measurement of the speed at which red blood cells settle to the bottom of a tube of blood in one hour - which indicates inflammation.

Blood testing can also reveal the presence of anemia, a condition in which there is a lack of healthy red blood cells to carry adequate oxygen to tissues. The chronic inflammation of AS may cause anemia.

Other tests may be ordered if a patient has symptoms suggesting a disorder related to AS, such as a colonoscopy for inflammatory bowel disease.

Treatment options for ankylosing spondylitis

Various treatments can help reduce the pain and stiffness associated with ankylosing spondylitis (AS). For example, exercise and movement help maintain the flexibility of the spine. Swimming is a preferred exercise for AS patients, according to the American Academy of Orthopaedic Surgeons.

The earlier treatment begins, the more effective it is likely to be. It is important that patients seek medical care before AS may cause irreversible damage to the joints.

Treatments used for AS include:

  • Nonsteroidal anti-inflammatory drugs (NSAIDs). NSAIDs can help relieve inflammation, pain and stiffness.
  • Disease-modifying antirheumatic drugs (DMARDs). These drugs are used to treat inflamed joints and other tissues. Potential side effects include stomach pain and increased risk of infections.
  • Corticosteroids. These medications may suppress inflammation and slow joint damage in advanced cases of ankylosing spondylitis. These drugs are usually taken orally but can also be injected. They should be taken for only a short time under close supervision of a physician, as potential side effects of long-term use include osteoporosis, fractures and diabetes.
  • Tumor necrosis factor (TNF) inhibitors. Originally used to treat rheumatoid arthritis, these drugs, a subgroup of biologic response modifiers (BRMs), may decrease inflammation, pain and stiffness in people with AS. Potential risks of TNF inhibitors include serious infections.

Patients frequently will also undergo physical therapy and rehabilitation. This can help improve physical strength and increase flexibility, which may lessen the pain associated with AS. Patients may learn range-of-motion and stretching exercises, which can help increase the flexibility of joints. They may also learn breathing exercises to help them sustain lung capacity, which can be damaged by AS.

Therapeutic use of water (hydrotherapy) and heat (thermotherapy) may also help.

Patients may learn proper sleep and walking positions to help them maintain proper posture and ergonomics. Using a proper chair, bed, mattress and pillow also help in maintaining normal ergonomics. Abdominal and back exercises can also help these efforts. When AS progresses, the upper body tends to stoop forward, but these exercises can help prevent that from occurring. Patients who have difficulty performing daily tasks may be referred to occupational therapy.

AS does not usually require surgery. However, an operation may be recommended for patients with severe pain or joint damage. Depending on the area affected, possible options may include spinal osteotomy, vertebral column resection, hip replacement or knee replacement, according to the American Academy of Orthopaedic Surgeons.

Most patients with ankylosing spondylitis remain employable and continue to function well in society. Education about the disease is essential in the treatment of AS.

Prevention methods for ankylosing spondylitis

Ankylosing spondylitis (AS) has a strong genetic component, but there is no known way to prevent the disease. However, patients who are aware of a family history of this disease can watch for signs and symptoms. Early detection of AS provides the best chance to treat the disease before it causes irreversible damage.

In addition, patients who are diagnosed with AS can help reduce the chance of further damage by quitting smoking. Patients with AS sometimes develop stiffness in the rib cage that reduces their ability to breathe fully. Damage to the lungs caused by smoking can worsen these symptoms. Researchers have also found smoking to be a risk factor for other forms of arthritis, including rheumatoid arthritis and osteoarthritis.


Questions for your doctor

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about ankylosing spondylitis (AS):

  • Do my symptoms suggest AS?
  • Is it true that blood tests can help reveal my risk level for AS?
  • What other tests for AS might I need to undergo, and what do they involve?
  • What do my test results show?
  • What areas of my body can AS affect?
  • Could I also have a condition related to AS, such as psoriatic arthritis, Reiter's syndrome or inflammatory bowel disease?
  • What are my treatment options?
  • Which medications do you recommend? What are their risks and benefits?
  • Do you suggest physical therapy, hydrotherapy, thermotherapy or similar treatments?
  • Does my prognosis improve if treatments are started early?
  • Could surgery become necessary to treat my AS?
  • Are there things I can do to prevent AS or its complications?

Additional Information


Ibuprofen Naproxen

What might complicate it?

Fractures of the spine can occur without any injury. Heart disease occurs in a small minority of individuals with long standing, severe disease. Inflammation of the eye (anterior uveitis) is associated in as many as 25% of cases. Formation of fibrous tissue in the lungs (pulmonary fibrosis) may occur, usually long after the onset of skeletal symptoms. Pneumonia is more common than in the general population.

Predicted outcome

The majority of individuals with ankylosing spondylitis are able to live normal lives. In recent studies, only ten to twenty percent become significantly disabled over a period of 20 to 40 years. A pattern of disease progression usually emerges after the first ten years.


Other disorders that have common presenting features are Reiter's syndrome, psoriatic arthritis, and the arthritis associated with inflammatory bowel disease. There are many other causes of spine pain that don't involve inflammation of the joints between vertebrae.


Physical therapy (heat packs, electrostimulation, deep breathing, back extension exercise), three times a week, for a period of four weeks.

Appropriate specialists

Rheumatologist, ophthalmologist, orthopedic surgeon, and physiatrist.