Where Does Ankylosing Spondylitis Start, and How Does It Progress?

In ankylosing spondylitis (AS), ongoing spine inflammation leads to stiffness, and in severe cases, the vertebrae (small spine bones) will start to fuse (grow together). When spine fusion occurs, the spine becomes inflexible. 

Most people with AS will experience periods of back pain and stiffness that come and go, called flare-ups. They will also experience periods of remission in which symptoms are either completely gone or milder. AS is a progressive condition, which means it gets worse with time. 

Symptoms of AS include back and hip pain, stiffness, fatigue, and reduced mobility. Treatment in AS is vital as untreated or undertreated disease can cause the condition to progress and damage the spine.

This article covers how ankylosing spondylitis starts, its stages, progression, and when to seek care. 

Where Ankylosing Spondylitis Starts

The earliest symptoms of AS are inflammatory low back pain and stiffness. Back pain and stiffness are typically worse in the morning and after periods of inactivity. 

Symptoms of AS will develop gradually over months or years. Symptoms might be worse in the morning and after periods of inactivity. 

Sacroiliac Joint Pain

Sacroiliitis, which is inflammation of one or both sacroiliac (SI) joints, affects around 10% of people with AS. The SI joints are located at the lower part of the spine where the spine and pelvis meet. For people with AS who experience sacroiliitis, it will occur early in the disease process and might be seen in imaging studies.

Sacroiliitis pain causes pain in the buttocks, low back, legs, hips, and feet. The pain can worsen after standing too long, going up or down steps, or walking long distances.

Other Early Signs

The earliest symptoms of AS will develop slowly over many months and years. In addition to back pain and stiffness, early AS causes:

• Arthritis: AS causes peripheral arthritis in the large joints of the arms and legs. According to a study reported in 2021, the prevalence of peripheral arthritis in AS ranges from 22% to 30%. Affected joints will be painful, tender, swollen, and warm to the touch. 
• Enthesitis: AS causes inflammation of the entheses—the areas where tendons and ligaments connect to bone. Common sites for enthesitis are behind the heel at the Achilles tendon, under the heel, where the ribs meet the breastbone, and in the spine, pelvic bones, and sacroiliac joints.
• Fatigue: This is a common symptom of AS, affecting 50% to 70% of people with the condition. People with AS experience fatigue very early on in the disease process. AS fatigue differs from simply feeling tired, and sleep doesn’t resolve it. It can affect many aspects of your life, including work and personal relationships. 
  

Stages of Ankylosing Spondylitis

AS progression can be measured in three stages—early, progressing, and advanced.

Early Ankylosing Spondylitis

For most people, AS starts in the low back and SI joints, causing pain and stiffness. They will also experience other early signs of AS, including fatigue, fever, appetite loss, and enthesitis. 

Not everyone will have the same symptoms in this early stage. People assigned female at birth might experience different symptoms, such as pain and stiffness of the neck rather than the back. They might also experience more peripheral joint pain than people assigned male at birth.

Progressing Ankylosing Spondylitis

As ankylosing spondylitis progresses, other joints and body tissues (i.e., muscles and tendons) will be affected. AS might also affect the organs, including the eyes, heart, and lungs, and cause stomach lining inflammation.

Eye inflammation: AS can lead to inflammatory eye conditions like iritis (inflammation of the colored ring of the eye) and uveitis (inflammation of the middle layer of tissue in the eye wall). Both conditions can cause blurred vision, sensitivity to light, eye pain, and eye dryness.

Left untreated, ongoing eye inflammation might lead to vision problems, including vision loss. Healthcare providers typically treat eye inflammation in AS with corticosteroid drops.

Heart complications: A small number of people with AS will experience cardiovascular troubles associated with the condition. Heart conditions linked to AS include aortitis (inflammation of the aorta), aortic valve disease, conduction disturbances, cardiomyopathy (damage to the heart muscle), and ischemic heart disease (blockage of blood flow to the heart muscle).

Gastrointestinal troubles: AS can affect the stomach lining and lead to inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis. Even without stomach inflammation, AS can cause gastrointestinal symptoms like bloating, constipation and diarrhea. 

Lung fibrosis: This is a rare complication that may be seen in the advanced stages of AS. There is a thickening of the pleura (the linings around the lungs) at the top of the lungs and thickening/scarring of the lung tissue beneath the pleura.

Advanced Ankylosing Spondylitis

In advanced AS, new bone formation called ankylosis causes the spine to fuse. Spinal fusion leads to spinal immobility and kyphosis (rounding of the upper back) and increases the risk of spinal fractures.

Fusing of vertebrae in the spine can prevent the rib cage from properly expanding, making it harder to take deep breaths. Kyphosis can lead to the appearance of the body being bent forward. The fusing also increases the risk of spinal fractures.

If there is scarring at the spinal nerves, you might experience neurological problems, including cauda equina syndrome (CES). CES is a rare symptom of AS, but because it is a medical emergency, it is still crucial to be aware of its symptoms. Symptoms include pain and weakness of the legs, urinary and bowel problems, and sexual dysfunction. 

If you experience symptoms of CES, you should call 911 or head to your local emergency department.

How Does AS Progress?

How AS progresses or changes over time will vary from person to person. Some people will experience only back pain and stiffness that comes and goes, while others will have mobility problems and experience signs of worsening disease.

According to findings of an observational study reported in 2019 in Arthritis Care & Research, at least 25% of people with AS experience disease progression.

The report’s authors note predictive factors in disease progression, including being assigned male at birth, joint damage at diagnosis, active disease, smoking, and higher inflammatory markers (findings in the blood that signify inflammation). 

Around 20% to 50% of AS study participants had some degree of spinal progression within two years following their diagnosis. Researchers also found treatment with tumor necrosis factor (TNF) inhibitors slowed the progression rate and reduced the potential for spine damage. These drugs include Enbrel (etanercept), Remicade (infliximab), Humira (adalimumab), Simponi (golimumab), and Cimzia (certolizumab)

Other treatments to slow progression include:

• Nonsteroidal anti-inflammatory drugs (NSAIDs) such as Advil (ibuprofen), Aleve (naproxen), Voltaren (diclofenac), Mobic (meloxicam), Celebrex (celecoxib)
• Interleukin-17 (IL-17) blockers, such as Cosentyx (secukinumab), Taltz (ixekizumab)
• Janus kinase inhibitors, such as Xeljanz (tofacitinib)
  

While ankylosing spondylitis can progress and worsen, it can also go into remission, which means having few or no symptoms. If you are in remission, make sure you keep following your treatment plan. Research shows people in AS remission who stop taking their medications will see their symptoms return quickly.

You can ask your healthcare provider to lower some medication doses while in remission, but do not make changes to your treatment plan without first talking to your healthcare provider. Contact them if symptoms of AS return, especially low back and peripheral joint inflammation. 

When to Seek Care

If you have not previously been diagnosed with AS and experience persistent back pain that is worse in the morning and improves with movement, you should reach out to a healthcare provider. You should also seek medical attention for eye symptoms, especially swelling, redness, and sensitivity to light. 

If you have AS and are seeing a specialist called a rheumatologist, reach out if you notice new or worsening symptoms. A rheumatologist is a specialist who diagnoses and treats arthritis conditions, including inflammatory arthritis conditions like AS.

You should reach out to your rheumatologist right away for the following symptoms:

• Breathing problems 
• Stiffening or immobility of the spine 
• Chest pain
• Vision problems
• Severe back or joint pain
• Unexplained weight loss

Summary 

Ankylosing spondylitis affects the joints and ligaments of the spine. Chronic inflammation can lead to spine stiffness, fusing, and fractures over time.

The earliest symptoms of AS are back and hip pain, peripheral arthritis, chronic fatigue, and inflammation of entheses. Symptoms will start slowly and worsen over months and years.

AS is a progressive condition, which means it gets worse with time. AS progression falls into three stages—early, progressing, and advanced. Treatment can slow down progression.

You should reach out to a healthcare provider if you experience persistent back pain that is worse in the morning and improves with movement. Contact a healthcare provider immediately if you have received a diagnosis of AS and experience worsening symptoms.

A Word From Verywell 

There is no cure for ankylosing spondylitis, but the condition is treatable and manageable. And, thanks to treatment advances, AS typically does not lead to any severe problems. 

Even so, it is still vital that you take all medications as prescribed and follow all your healthcare provider’s instructions. Go to all appointments and keep up with follow-up testing if even you feel better or have no symptoms. This is the best way to improve your outlook and quality of life despite AS.