How Does Ankylosing Spondylitis Progress?

Reviewed by: HU Medical Review Board | Last reviewed: February 2019 | Last updated: October 2021

Ankylosing spondylitis (AS) is a chronic inflammatory arthritis that typically begins in teens or young adults, with most beginning to have symptoms between the ages of 20 and 30.1 When considering the progression of AS, it's important to note that there is wide variation between different individuals with AS. Some people may experience rapid progression while others experience a mild or slower progression.

While the disease is chronic and may progress and cause joint damage and disability, some with AS may never experience significant joint damage, and early and effective treatment may help prevent or slow joint damage. There is no single pattern of progression that applies to everyone with AS, but some of the common ways the disease can progress are described below. Ankylosing spondylitis is rarely diagnosed early, and the interval between the first symptoms and diagnosis may take, on average, 4-9 years.

What are the stages of ankylosing spondylitis

Some researchers have described that AS progresses through three stages which are on a continuum. In the first stage, the person is having symptoms, such as chronic pain in the low back, but there is no evidence of joint involvement on x-rays, called "radiographic evidence." Magnetic resonance imaging (MRI) may show abnormalities in this early stage.2

In the second stage, joint involvement, particularly in the sacroiliac joints (located between the pelvis and spine), is visible on x-rays. Along with the symptoms of AS, these features make AS more likely to be diagnosed at this stage.2

In the third stage, joint damage has occurred and is irreversible. The chronic inflammation of the joints causes bone loss, and as the body rebuilds this bone tissue, new bony tissue encompasses where the ligaments attach to the joint. The calcification of the spinal ligaments is called syndesmophytes. As the condition develops and the spine becomes more immobilized by the formation of bone in the joints, the spine can take on the appearance of bamboo on x-rays and is referred to as "bamboo spine." The presence of bamboo spine increases a person's risk of fractures in the vertebrae.2,3

How does ankylosing spondylitis progress?

Despite the three stages described above, it is important to note that not all people with AS will have this progression. One study found that 1 in 4 patients with AS do not show progression seen on x-rays.4 Some factors that have been associated with more progressive or severe disease include gender and an early age when symptoms begin. Men are more likely to have more severe disease. In women, AS is more likely to be associated with a later onset, milder symptoms, and have symptoms affecting other parts of the body than the spine, such as inflammation in the eyes (uveitis) and arthritis in the peripheral joints. While AS symptoms may be milder in women than in men, studies have found that women with AS have symptoms that affect their day-to-day lives more.2

Early signs of ankylosing spondylitis

In most people with AS, symptoms begin in the low back and sacroiliac joints. This can cause pain and stiffness in the low back or hips, and the pain is usually worse after periods of inactivity, such as in the morning after a night's sleep. Symptoms usually improve with activity. Early symptoms can also include fatigue, a mild fever, or loss of appetite.5,6

In addition to the sacroiliac joints, many people with AS have inflammation in the locations where the ligaments and tendons attach to the bone. This inflammation is called enthesitis and can cause "hot spots" of tenderness along the spine or along the back of the heel.5,6

Not everyone has the same early symptoms, though, and women with AS may have different symptoms, such as pain and stiffness in the neck rather than the lower back. In a small percentage of people with AS, symptoms may begin in a peripheral joint, such as the hip, knee, shoulder, or elbow.5

Additional symptoms

In addition to the joints, AS can cause inflammation in other parts of the body. Many people with AS also have inflammatory bowel disease, such as Crohn's disease or ulcerative colitis. Some people experience inflammation in their eyes (uveitis or iritis) or skin.5,7

Flares and remission

AS is a chronic condition, and people with AS may experience flares (periods of increased symptoms or when symptoms are worse) and times of remission (periods when symptoms lessen or go away). Flares may be localized to one area or they may be felt throughout the body, and they may last a few days or a few weeks. Localized flares are increased pain or stiffness in one area of the body, while generalized flares can cause pain throughout the body, fatigue, or emotional symptoms such as depression or anger.8,9 One survey of people with AS found that most people believed their flares were triggered by an increase in stress or "overdoing it," but the majority also reported no long-term effects following a flare.8

Long-term prognosis of ankylosing spondylitis

Because AS tends to begin in adolescence or young adulthood, there is a prolonged stress of the disease on the body compared to other types of arthritis. The chronic inflammation that occurs with AS can affect the whole body, not just the joints, and researchers have linked AS with a higher risk of heart disease as well as a higher mortality rate from heart disease. Both men and women with AS have an increased risk of developing heart disease, such as coronary heart disease. Also, if they have a cardiovascular event (like a heart attack or stroke), these events are more likely to be fatal.10,11

What's the life expectancy with AS?

Several studies have found a link between heart disease and AS, showing that people with AS are more likely to develop heart disease and more likely to die from cardiovascular events.10-13 To date, a specific life expectancy for people with AS has not been established. However, proper diagnosis and treatment for AS are important not only to slow or stop the joint progression and possible disability but also to reduce the widespread inflammation in the body that can lead to complications such as heart disease.

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