Ankylosing spondylitis (AS) is a form of arthritis that mainly affects the spine, lower back, and sacroiliac joints.

doctor performs a physical exams to help diagnose ankylosing spondylitisShare on Pinterest
1153626202 Image credit: Ngampol Thongsai / EyeEm / Getty Images.

AS is an inflammatory condition. Characteristic symptoms include joint pain, stiffness, and a loss of mobility in the spine and lower back.

The condition involves inflammation where the ligament and tendons attach to the bones of the spine and the bones of the peripheral joints, known as the entheses.

This inflammation results in increased bone formation in the spine, leading to bone fusion. In advanced cases, this can also lead to spinal deformity.

Drug treatments and physical therapy can help relieve the symptoms.

This article explains AS, including its symptoms, treatments, causes, complications, and associated exercises.

A diagram showing the differences between a regular spine and the spine of a person with ankylosing spondylitis (AS). In AS, the vertebrae are inflamed and fused together. The natural curvature of the spine is also affected. Share on Pinterest
A diagram showing the differences between a regular spine and the spine of a person with ankylosing spondylitis (AS). In AS, the vertebrae are inflamed and fused together. The natural curvature of the spine is also affected. Infographic by Jason Hoffman.

AS is a type of arthritis. It mostly affects the lower part of the spine and where the spine joins to the hips, known as the sacroiliac joints.

AS can be challenging to diagnose, but it has a particular pattern of pain symptoms, and the changes are usually visible in X-ray and MRI scans.

Males are more likely to develop AS than females. According to the Spondylitis Association of America (SAA), symptoms usually begin between the ages of 17 and 45 years.

However, symptoms can also develop in children and people who are much older.

There is currently no cure for AS, but certain drugs can help manage pain and inflammation. Physical therapy can relieve pain and prevent or delay limitations and decreased mobility.

The most common early symptoms of AS are frequent pain and stiffness in the lower back, the hip area, or both. These symptoms may occur over several weeks or months.

Over time, these symptoms may spread to other areas of the spine and can affect the neck’s spinal joints.

Some people have mild pain that comes and goes, while others have severe, long lasting pain. Everyone with AS is likely to experience flares — when the symptoms worsen — and periods of remission where symptoms improve.

The main symptoms of AS affect the spine and lower back, causing:

Learn more about the early signs of AS.

The pain usually worsens at rest and during the night and can interfere with restorative sleep. Moving around can generally improve pain levels.

However, AS can also affect other parts of the body. These include the areas around other joints, such as the:

  • ribs
  • shoulders
  • knees
  • ankles, feet, and tendon insertions at the heel
  • top of the shin bone in the lower leg
  • Achilles tendon

AS is a systemic condition. People can experience fatigue, which refers to a feeling of being tired and lacking energy.

Learn more about how to recognize symptoms of AS.

There is currently no cure for AS. However, treatment can help relieve symptoms and manage the condition’s progression.

Treatment options include:

People with a diagnosis of AS will need to consult a specialist doctor known as a rheumatologist. They may need several visits as the condition progresses slowly, and consistent medical care allows better monitoring and treatment.

Doctors will only recommend surgery to correct severe deformities, such as excessive posture changes due to inflammation and ankylosing of the spine, or replace a hip or other joint.

Doctors might also recommend certain diets, foods, or nutrients to help a person manage the symptoms of AS.

Learn more about diet and AS.

Drug treatment

The main drugs that people use to ease the pain and inflammation of AS are nonsteroidal anti-inflammatory drugs (NSAIDs). Some examples include:

Acetaminophen and codeine are also options if NSAIDs are unsuitable or ineffective.

Some NSAIDs compromise bone health by reducing the creation of new bone, so doctors do not usually recommend NSAIDs after surgery for people with bone fusion problems.

Some other drug options and their examples include:

AS can affect the whole body, and a person may require coordination of care by several specialists, including:

Learn more about the drug treatments for AS.

To diagnose AS, a doctor will ask about the person’s symptoms, perform a physical examination, and arrange for tests when necessary.

If inflammatory back pain is present with certain features, it may indicate AS.

These features include:

  • pain that does not improve with rest
  • pain that causes sleep disturbance
  • back pain that starts gradually, between the ages of 17 and 45 years, and is not due to injury
  • symptoms that persist for several months
  • spinal stiffness in the mornings, which seems to improve with exercise and motion

Imaging tests for AS may confirm the diagnosis, but changes may not be immediately visible on such tests. This can delay diagnosis.

The section below examines blood and imaging tests in more detail.

Learn more about the diagnostic criteria for AS.

Blood tests

No blood test can confirm AS, but some tests can rule out other causes of the person’s symptoms.

A reported 90% of people with AS have a genetic marker called HLA-B27. Doctors may order a blood test for this as a part of the initial workup.

The tests for inflammation may include:

Imaging tests

These may include:

  • X-rays: These can reveal both early and more advanced changes to the spine and pelvis.
  • CT scans: This creates more reliable, higher resolution images than X-rays.
  • MRI scans: For example, an MRI of the sacroiliac joints can reveal early signs of AS.

The exact cause of AS remains unclear, but the early symptoms result from inflammation in parts of the lower spine.

AS may have genetic and environmental components. Researchers believe that people with certain genes may develop AS after exposure to a trigger, such as a virus or bacteria.

About 90% of people with AS have the HLA-B27 gene, and the condition often runs in families.

A common complication of AS is inflammation of the eyes, causing pain and redness. This inflammation, known as iritis or uveitis, can impair vision without treatment.

In severe cases, AS can cause the vertebrate of the spine to fuse together, or “ankylose.” This can make it challenging to perform everyday tasks. Fusion of the bones can also lead to curvature of the spine, although this is far less common now due to advances in treatment.

In some cases, AS can also restrict the movement of the chest and make it difficult to breathe.

If a person has had AS for a long time or the bones have fused together, they may also be at risk of fracturing bones in their back.

About 15% of people with AS experience jaw inflammation, making it difficult to open their mouths to eat. At the same time, around 6–14% of people experience inflammatory bowel disease (IBD).

Learn more about the effects of AS on the body.

Other rarer complications of the condition may include:

  • Aortic regurgitation: Where the heart’s aortic valve does not close tightly.
  • Pulmonary fibrosis: A type of lung disease where the tissue is damaged or scared.
  • Cauda equina syndrome: A complication where the nerves in the back become severely compressed.

Chronic pain and symptoms associated with AS can cause people to experience depression and other mood disorders.

Learn more about the possible complications of AS.

Although living with AS can present challenges, there are many ways that people can adapt to living with the condition.

According to the National Institute of Arthritis and Musculoskeletal Diseases (NIAMS), research shows that people who involve themselves in their care report less pain and enjoy a better quality of life.

There are many ways that people can practice self-care, including:

  • learning about the disease and its treatments
  • seeking support for the physical and mental effects of AS
  • communicating with health teams to enable the best care for their condition

People can also try numerous lifestyle changes and activities to improve function and increase their understanding and autonomy over their condition. These include:

The SSA offers further resources and support for people living with AS, including support groups, educational resources, and community forums.

Physical therapy and exercises can help treat the symptoms and prevent or delay mobility limitations.

A physical therapist will be able to design a program that can help a person maintain good posture and motion in the joints.

This might consist of the following:

  • daily exercises
  • special training to address areas of involvement
  • therapeutic exercises

Physical therapy exercises are known as strengthening exercises and range-of-motion exercises.

The SSA notes that an ideal exercise program will include the following four elements:

  • Stretching: This can improve flexibility and reduce muscle stiffness, swelling, and pain. It can also minimize the risk of joint fusion.
  • Cardiovascular exercises: These exercises include swimming and walking. They can improve lung and heart function and reduce pain and fatigue.
  • Muscle exercises: These help strengthen the core and back muscles, which help support the spine. Having strong muscles can improve posture and movement, as well as reduce pain.
  • Balance training: This can help improve stability and reduce the risk of falls.

Learn more about specific exercises for AS.

The outlook for AS is difficult to predict because it varies widely from person to person, and the progression is often not constant. Important factors for measuring outlook include levels of functional ability, spinal mobility, and joint damage.

Some people experience severe functional loss, while others hardly notice their symptoms. Around 1% of people experience long-term remission, wherein symptoms cease to develop. In contrast, some people may have life threatening complications that affect the heart, lungs, or nervous system.

Smoking can lead to poorer outcomes.

AS is a type of arthritis that affects the spine and lower back. It is most common in males and tends to appear in late adolescence or early adulthood.

Although there is currently no cure for AS, many treatments can help slow or stop the progression. Daily management, such as an exercise program, can help people control their symptoms.