David Ozeri, MD, is a board-certified rheumatologist from Tel Aviv, Israel specializing in arthritis, autoimmune diseases, and biologic therapies.

Ankylosing spondylitis (AS) is an inflammatory disease that can cause bones in the spine to fuse. Fusing causes the spine to be less flexible and can eventually lead to spinal stenosis in which the spaces in the spine narrow and compress the spinal cord and spinal nerve roots.

AS is characterized by chronic inflammation in vertebral joints of the spine and the entheses , the places where tendons and ligaments attach to bone. Joints are the points where two or more bones meet to allow movement.

Chronic inflammation will cause the wearing away of the bones and joints. When bone tissue is worn down, the body tries to create new bone, and fusing will then occur.

Spinal stenosis causes a pinching of the spinal cord and spinal nerves. This pinching results in symptoms of pain, cramping, weakness, and numbness felt in the lower back and legs, neck, shoulders, or arms.

Spinal changes from AS can lead to bony growths on the edges of bones (bone spurs), thickened ligaments, and bulging discs—all of which narrow the spaces of the spine. AS is linked to other spinal complications, including fractures and kyphosis.

This article discusses AS and its spinal complications, including the symptoms of spinal stenosis, available treatment, and prevention.

Most people with AS will never become disabled, or they will have a minimal disability. Some people with the condition will develop restricted spine movement from spine curvature, fractures, or spinal stenosis.

One study from Minnesota estimated that AS occurs in approximately three persons per 100,000 people per year. It usually is diagnosed in teenagers and young adults. But anyone, regardless of age, can be diagnosed with AS. It is three more than times more common in males than females.

Symptoms of AS will vary person-to-person, but most people with AS will experience:

Symptoms of AS will develop gradually, over several months or even years. They may come and go through periods of flare-ups (worsening symptoms) and remission (few or no symptoms).

With treatment, the condition can improve for most people. For others, however, it will gradually worsen even with treatment.

A spinal fracture is a crack or a break in the vertebrae. Spinal fractures can occur in the low back (lumbar ), mid-back (thoracic ), or neck (cervical spine).

Lumbar and thoracic fractures are more common, whereas cervical fractures are rarer and can be extremely dangerous and life-threatening. Spinal fractures vary in severity from mild to severe.

When AS leads to fused joints in the spine, the spine will lose its mobility and become stiff and unstable. The fused joints are weak and brittle, which increases the risk of fractures.

A spinal fracture in AS can occur from a traumatic injury, such as a fall, or with minor activity, such as reaching or bending. In people who have both AS and osteoporosis, the risk for fractures is even higher. Osteoporosis is a condition in which bones become weak and brittle. It is a frequent and early complication of AS.

A minor spinal fracture can go unnoticed. However, a severe fracture can cause severe pain and spinal cord damage. A fracture of the lumbar or thoracic spine can cause pain that gets worse with movement. This is different from AS pain, which improves with activity.

AS can cause the spine to become less flexible. A less flexible spine can cause a forward curvature called kyphosis . This is also a sign of severe AS.

Kyphosis can negatively affect a person's balance. It causes displacement of the person's center of gravity forward and backward in the sagittal plane—the hypothetical plane used to transect the body into right and left parts. Kyphosis also causes the lower extremities (from the hips to the toes) to compensate for your center of gravity.

People with kyphosis might experience the following symptoms:

Early diagnosis offers the best outlook for someone with kyphosis. Treatment can reduce further problems and the need for surgery. Untreated kyphosis will worsen and lead to health problems that interfere with life quality.

Spinal stenosis refers to the narrowing of the spaces within the spine. That narrowing causes pressure on the nerves that travel through the spine.

There are two main types of spinal stenosis based on the part of the spine they affect, which are:

Cauda equina syndrome (CES) is a condition that causes compression of the cauda equina, the collection of nerves at the end of the spinal cord. It is a rare and serious condition. It is also a medical emergency.

Lumbar stenosis is a risk factor for CES. Symptoms of CES might be similar to those of spinal stenosis and should not be ignored.

It is possible to have spinal stenosis and not notice symptoms. For many people, the first time they learn they have this condition is after a computed tomography (CT) scan or magnetic resonance imaging (MRI). When symptoms occur, they worsen with time. Symptoms vary based on the location of the stenosis and affected nerves.

Symptoms of lumbar stenosis include:

Symptoms of cervical stenosis include:

You should see your healthcare provider if you experience any of the signs of spinal stenosis, even if you do not have AS.

To diagnose spinal stenosis, your healthcare provider will ask you about the symptoms you are experiencing and your medical history. They will also conduct a physical exam.

In a physical exam, the provider will examine your spine for spinal abnormalities, such as atypical curvatures, kyphosis, and areas of swelling, tenderness, and pain. They will also want to observe your posture and how you stand, sit down, and walk. You will be asked to bend forward, backward, and side-to-side.

Your healthcare provider will also order imaging tests to pinpoint the cause of signs and symptoms. This might include X-rays, MRIs, or CT scans.

Treatment for spinal stenosis will depend on the area of the spinal cord affected and how severe pain and other symptoms are.

If you are not experiencing any pain or other symptoms, your healthcare provider will monitor your condition with follow-up visits and testing. They also recommend self-care tips to prevent pain or any further damage to the spine.

If you are experiencing symptoms of spinal stenosis, your healthcare provider will recommend medicines, physical therapy, and nonsurgical therapeutic procedures.

Medicines to help manage spinal stenosis pain and other symptoms include:

Physical therapy can help you manage pain and other symptoms of spinal stenosis. A physical therapist can recommend exercises to build up your strength and endurance, improve your balance, and maintain spine flexibility and stability.

Two commonly used nonsurgical procedures for spinal stenosis are epidural steroid injections and decompression procedures.

Your healthcare provider might recommend surgery for spinal stenosis if other treatments have not worked or symptoms are severe and disabling. The goal of surgery is to relieve pressure off the spinal cord or nerve roots by creating more space.

A spinal fracture might take weeks or months to heal. Your healthcare provider might recommend you:

Treatment for kyphosis depends on the cause and the severity of symptoms.

Your healthcare provider might recommend:

The main goal of treating AS is to prevent joint damage to the spine. You will want to follow your treatment plan exactly as prescribed and reach out if you do not see improvement or if symptoms are getting worse.

Additional ways to protect your spine include:

Ankylosing spondylitis is an inflammatory disease of the spine. Thanks to advanced treatment options, most people with AS will never become disabled. However, some people with AS might experience the restricted movement of the spine, spine fractures, and nerve root compression.

Fortunately, many of the complications of AS, including spinal stenosis, can be managed and treated. But it is crucial to get treatment to avoid disability. Spinal complications of AS might be preventable with different methods, including staying active, protecting your joints, not smoking, avoiding alcohol, and getting plenty of calcium and vitamin D.

Ankylosing spondylitis can impact your health in many ways. Therefore, it is essential to have a team of healthcare providers to treat AS and your overall health.

The most important person to include on your healthcare team is a rheumatologist—a doctor specializing in musculoskeletal disease and systemic diseases of the joints, muscles, and bones. Other specialists to include are a physical therapist and occupational therapist.

If you find you are experiencing emotional effects, your rheumatologist or primary healthcare provider can recommend a mental health therapist.

They are different conditions, and spinal stenosis can be a complication of AS. AS affects the entire spine, whereas spinal stenosis affects the spaces between the individual bones of the spine, either at the low back or at the neck.

Spinal stenosis causes narrowing of those spaces, which puts pressure on the nerves and leads to symptoms of numbness, weakness, and pain.

Autoimmune diseases that affect the spine, such as ankylosing spondylitis and rheumatoid arthritis, can lead to spinal stenosis. This is often the result of chronic inflammation of the small bones of the spine, which leads to bone loss, bony growths, thickened ligaments, and bulging disks.

Both ankylosing spondylitis and spinal stenosis are serious conditions that require treatment. Untreated AS can lead to severe spine complications, including spinal stenosis, kyphosis, and spinal fractures. On the other hand, untreated spinal stenosis can cause permanent nerve damage that might lead to paralysis or death.

Spine narrowing in ankylosing spondylitis can occur in the spaces between the vertebrae as a result of chronic inflammation. Treatment with disease-modifying antirheumatic drugs (DMARDs) can reduce the potential for this disease complication.

"Cervical stenosis" is the name for spinal stenosis of the neck. It causes neck pain and numbness, tingling, and weakness of an arm, hand, leg, or foot.

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