Axial spondyloarthritis is a chronic inflammatory disease that primarily affects the spine and surrounding joints, causing pain and stiffness that often begins in young adulthood. While there is no cure, understanding this condition and working with healthcare providers can help people manage symptoms and maintain an active, fulfilling life.
What Is Axial Spondyloarthritis?
Axial spondyloarthritis, often shortened to axSpA, is a type of inflammatory arthritis that affects the joints in your axial skeleton. The axial skeleton includes your chest, spine, and pelvis. This condition causes pain, stiffness, and swelling in these areas, particularly in the lower back and the joints where the spine connects to the pelvis, called the sacroiliac joints.[1]
What makes axSpA different from other types of arthritis is that it can affect more than just your joints. The disease is considered systemic, meaning it can impact other parts of your body and organs. For example, you might experience eye inflammation, digestive problems, or skin changes that seem unrelated to joint pain, but are actually part of the same condition.[2]
Axial spondyloarthritis is an umbrella term that includes two main types of the disease. The first type is ankylosing spondylitis, also called radiographic axSpA, where damage to the sacroiliac joints and spine can be seen on X-rays. The second type is non-radiographic axial spondyloarthritis, where X-ray changes are not present but inflammation may be visible on MRI, or you have symptoms even without visible inflammation.[4]
These two forms are part of the same disease family and share many features. However, they also have some differences. For example, the disease process and how it appears on medical imaging can vary between the two types. Some people with non-radiographic axSpA may never develop visible damage on X-rays, while others may eventually progress to the radiographic form.[8]
Over time, if left untreated, axSpA can cause the bones of your spine to grow together and fuse. This process is called ankylosis. When this happens, the spine becomes stiff and less flexible, which can make it harder to move and can lead to a hunched posture. The fusion can also cause osteoporosis in your spine, making the bones weaker and increasing the risk of fractures.[1]
How Common Is Axial Spondyloarthritis?
Axial spondyloarthritis affects approximately one in every hundred people, which means around 3 million people in the United States live with this condition. While this may sound like a large number, it remains relatively unknown compared to other diseases, and many people have never heard of it before receiving their diagnosis.[6]
Globally, axSpA affects about one percent of the population. The disease shows some variation across different populations and regions, which researchers believe may be related to genetic factors and other regional influences. These variations in how common the disease is across different groups help scientists understand more about what causes axSpA.[1][7]
When it comes to who gets axSpA, there are some interesting patterns. The disease usually begins in people younger than 40, often starting during the teenage years or in the twenties. It’s less common for symptoms to first appear after age 45. Unlike many other rheumatic conditions, axSpA occurs equally in males and females overall. However, when looking at the specific types, ankylosing spondylitis is more common in men than women, while non-radiographic axSpA may be just as common in women as in men.[2][7]
The disease is less common among African Americans compared to people of other racial backgrounds. This difference in how frequently the condition appears in different populations provides clues about the genetic and environmental factors that may contribute to developing axSpA.[2]
What Causes Axial Spondyloarthritis?
The exact cause of axial spondyloarthritis is not completely clear, but researchers have identified several factors that play important roles in who develops the disease. Genetics appears to be a major contributor. AxSpA often runs in families, suggesting that inherited factors significantly influence whether someone will develop this condition.[1]
Most people with axSpA carry a gene called HLA-B27. This gene is strongly associated with the disease, particularly with ankylosing spondylitis. However, having this gene does not mean you will definitely get axSpA. Many people carry the HLA-B27 gene and never develop the condition. At the same time, some people develop axSpA without having this gene at all, showing that other factors must also be involved.[1][2]
The HLA-B27 gene is more prevalent in people with radiographic axSpA compared to those with non-radiographic axSpA. This difference helps explain some of the variations between these two forms of the disease.[12]
Beyond HLA-B27, other genetic factors are likely involved in the development of axSpA. Research suggests that genes influencing how the body presents antigens to the immune system and genes related to inflammatory pathways, particularly those involving interleukin-23 and interleukin-17, may also play a role.[7]
Researchers believe that people with certain genes develop axSpA when they are exposed to specific triggers. These triggers might include viruses, bacteria, or other environmental factors. However, the exact triggers remain under investigation, and scientists are still working to understand how genes and environment interact to cause the disease.[2]
The disease involves an overactive or unregulated immune system. In axSpA, the immune system, which normally fights infections, begins attacking the body’s own tissues. This autoimmune response leads to inflammation in the joints and other tissues. The inflammation particularly affects areas where ligaments or tendons attach to bone, sites called entheses. This inflammation at the entheses is a hallmark feature of the disease.[4][6]
Who Is at Risk for Developing Axial Spondyloarthritis?
Several factors can increase your risk of developing axial spondyloarthritis. Understanding these risk factors can help in early recognition and diagnosis of the condition.
Family history is one of the strongest risk factors. If you have close relatives with axSpA or related conditions like psoriatic arthritis or inflammatory bowel disease, your risk of developing the condition is higher. The tendency for axSpA to run in families highlights the important role that genetics plays in the disease.[2]
Age is another significant factor. The disease most commonly begins between ages 20 and 40, with many people experiencing their first symptoms during their teens or twenties. While it’s possible to develop axSpA at other ages, having persistent back pain that starts before age 45 is considered one of the key features of the disease.[2][3]
Carrying the HLA-B27 gene increases your risk, although most people with this gene never develop axSpA. If you have the gene and also have a family history of the disease, your risk is higher than someone with just one of these factors.[3]
Smoking can worsen the disease in people who already have axSpA. Smokers with axial spondyloarthritis tend to experience earlier onset of back pain, higher disease activity, more inflammation in the spine, greater structural joint damage, and poorer quality of life compared to non-smokers with the condition. This makes smoking cessation an important part of managing axSpA if you do develop it.[18]
People who experience recent infections or trauma may be more likely to have disease flares if they already have axSpA, though whether these factors contribute to initially developing the disease is less clear. Emotional stress and major life changes can also trigger symptom flares in people living with the condition.[22]
What Are the Symptoms of Axial Spondyloarthritis?
The symptoms of axial spondyloarthritis can vary from person to person, but there are several characteristic features that help identify the condition. Understanding these symptoms is important for recognizing when to seek medical attention.
The most common symptom of axSpA is back pain, particularly in the lower back, buttocks, and hips. However, this is not ordinary back pain. The pain associated with axSpA has specific characteristics that distinguish it from other causes of back discomfort. This type of pain is called inflammatory back pain, and it has features that set it apart.[1][2]
Inflammatory back pain develops slowly over weeks or months rather than appearing suddenly. It is chronic, meaning it lasts for three months or longer. The pain is not caused by an injury or mechanical problem like a slipped disk or muscle spasm. One of the most telling features is that the pain and stiffness are worse in the morning or after periods of rest, but they improve with exercise and movement. This is opposite to mechanical back pain, which typically worsens with activity.[1][3]
Stiffness, especially early-morning stiffness, is another hallmark symptom. Many people with axSpA wake up with significant stiffness in their back that can last for an hour or more. This stiffness gradually wears off or reduces during the day as they move around and stay active.[2][4]
The pain and stiffness can occur anywhere in the spine, but they often start in the sacroiliac joints, where the pelvis connects with the tailbone. The pain may spread to other areas, including the hips, buttocks, neck, shoulders, upper back, and ribcage. Some people experience pain during the night or in the early morning hours that can disrupt their sleep.[2][3]
Beyond the spine, axSpA can affect other joints and areas of the body. The condition may cause pain and swelling in peripheral joints such as the knees, ankles, heels, or toes. Enthesitis, which is inflammation where tendons attach to bone, commonly affects the Achilles tendon at the heel. Dactylitis, an inflammation of entire fingers or toes that makes them appear swollen like sausages, can also occur.[1][2]
Fatigue is a common and often underrecognized symptom of axSpA. The chronic inflammation in your body, combined with disrupted sleep from nighttime pain, can leave you feeling extremely tired. This exhaustion goes beyond normal tiredness and can significantly impact your daily life and ability to function.[1][2]
Because axSpA is a systemic disease, it can cause problems in other parts of the body. Eye inflammation, called uveitis or iritis, occurs in some people with axSpA. This causes eye pain, redness, sensitivity to light, and vision problems. The eye may look red, particularly the white part of the eye. Uveitis requires prompt medical attention to prevent complications.[1][2][3]
Digestive problems, including abdominal pain and diarrhea, can occur in people with axSpA. Some people with this condition also have or develop inflammatory bowel disease. Skin problems are another possible symptom, with some people experiencing psoriasis, a condition that causes red, scaly patches on the skin.[1][2]
Some people may experience appetite loss and weight loss, particularly in the early stages of the disease. You might also feel feverish or experience night sweats. These symptoms reflect the body-wide inflammation occurring with the condition.[4]
The symptoms of axSpA can come and go over time. You may have periods when symptoms are more active, called flares, and other times when symptoms are less noticeable or absent. The pattern and severity of symptoms can differ greatly from one person to another.[2]
How Is Axial Spondyloarthritis Diagnosed?
Diagnosing axial spondyloarthritis requires a combination of approaches, as there is no single test that can definitively confirm the condition. Doctors use your medical history, physical examination, blood tests, and imaging studies to make a diagnosis.
When you visit your healthcare provider about back pain, they will start by taking a detailed medical history. They will ask about the characteristics of your pain, when it started, what makes it better or worse, and whether you have morning stiffness. They will also ask about any family history of axSpA or related conditions, as well as any other symptoms you might be experiencing in other parts of your body.[1]
During the physical examination, your provider will check your vital signs and examine your spine and joints. They may test your range of motion, looking at how well you can move your spine and other affected joints. They will also look for signs of inflammation in your joints and check for tenderness in areas where tendons attach to bones.[1]
Blood tests play an important role in the diagnostic process. Your doctor may order tests to look for the HLA-B27 gene. While having this gene does not mean you definitely have axSpA, it provides supporting evidence when combined with your symptoms and other findings. Your doctor may also check for C-reactive protein, a marker of inflammation in your body. Elevated levels of this protein indicate that inflammation is present, though normal levels do not rule out axSpA.[1][3]
Imaging tests are crucial for diagnosing axSpA and determining which type you have. X-rays of your spine can show damage to the sacroiliac joints, a condition called sacroiliitis, which is a key sign of axial spondyloarthritis. X-rays can also reveal changes in the vertebrae and show if any fusion of the spine has occurred. However, it can take several years of ongoing inflammation before changes become visible on X-rays.[1][3][7]
Magnetic resonance imaging, or MRI, is another important imaging tool. MRI scans can detect inflammation and changes in the spine much earlier than X-rays can. This makes MRI particularly valuable for diagnosing non-radiographic axSpA, where X-ray changes may not yet be present. Around seven in ten people with non-radiographic axSpA have visible inflammation in the sacroiliac joints or spine on MRI scans.[1][4]
It’s important to understand that healthcare providers can diagnose axSpA based on your symptoms and clinical findings, even if imaging tests do not show inflammation. Some people have all the typical symptoms of inflammatory back pain and other features of axSpA, but their MRI scans appear normal. This can happen in about three out of ten people with non-radiographic axSpA, possibly due to limitations in the sensitivity of MRI or because inflammation varies over time.[4]
The diagnosis requires the doctor to assess all the information together, including your medical history, symptoms, physical exam findings, blood test results, and imaging studies. This comprehensive approach helps ensure an accurate diagnosis and allows treatment to begin as early as possible.[3]
How Can Axial Spondyloarthritis Be Prevented?
Because the exact cause of axial spondyloarthritis is not fully understood, and genetic factors play a significant role, there is currently no known way to prevent the disease from developing in the first place. However, there are important steps you can take to reduce your risk of complications and slow the progression of the disease if you do develop axSpA.
If you smoke, quitting is one of the most important things you can do. Smoking has been clearly linked to worse outcomes in people with axSpA. Smokers with the condition experience earlier onset of back pain, more severe disease activity including more pain, stiffness and swelling, increased inflammation in the spine, greater structural damage to joints, and significantly poorer quality of life. Stopping smoking can help improve these outcomes and make your condition easier to manage.[16][18]
Staying physically active and exercising regularly is essential for anyone with axSpA or at risk of the condition. Exercise helps maintain flexibility in your spine and other joints, preserving your range of motion. It also helps prevent the spine from becoming stiff and painful. Regular physical activity is not just recommended but is actually prescribed as a fundamental part of treatment for axSpA.[3][14]
Practicing good posture throughout the day can help prevent your spine from developing abnormal curves or a hunched position. This includes being mindful of how you sit, stand, and sleep. Using proper ergonomics at work and home can make a significant difference in maintaining spinal alignment.[16]
If you have a family history of axSpA or carry the HLA-B27 gene, being aware of the early symptoms of the disease can help you seek medical attention promptly if symptoms develop. Early recognition and treatment can help prevent or minimize long-term damage to your spine and joints.[7]
Managing stress through healthy coping mechanisms can be beneficial, as emotional stress can trigger symptom flares in people with axSpA. Finding ways to relax and maintain emotional well-being, such as through meditation, yoga, spending time in nature, or pursuing hobbies you enjoy, can help you manage the condition better.[16]
How Does Axial Spondyloarthritis Affect the Body?
Understanding what happens inside your body when you have axial spondyloarthritis can help you better understand your symptoms and why treatment is important. The disease causes changes in how your body normally functions, primarily through inflammation and the body’s response to that inflammation.
At the most basic level, axSpA involves inflammation occurring at specific sites in your body. The disease particularly affects areas called entheses, which are the points where ligaments or tendons attach to bone. This inflammation at the entheses is known as enthesopathy. Common sites include where the Achilles tendon attaches at the heel, where ligaments connect to the spine, and at the sacroiliac joints where the pelvis meets the spine.[4]
The inflammatory process in axSpA follows a pattern. First, inflammation occurs at the site where ligaments or tendons attach to bone. This inflammation causes pain, swelling, and stiffness. Next, the inflammation leads to some wearing away of the bone at the attachment site. As the inflammation eventually reduces, healing begins to take place, but this healing process involves the development of new bone.[4]
When new bone forms during healing, it can replace the elastic tissue of ligaments and tendons. This new bone growth restricts movement in the affected joints. If this inflammatory cycle repeats multiple times at the same location, more bone continues to form. Eventually, the individual bones that make up your backbone, called vertebrae, can fuse together. This fusion creates a rigid, less flexible spine.[4]
The fusion of vertebrae causes several problems. First, it greatly reduces your ability to bend and move your spine. The natural curves of your spine can flatten, which may lead to a hunched posture. If the rib cage is affected, the joints that allow your ribs to expand when you breathe can become stiff, making it harder to take deep breaths.[2][5]
The fusion process can also lead to osteoporosis in the spine. This means the bones become weaker and more fragile, even as parts of the spine are fusing together. The combination of stiffness and weakened bones significantly increases the risk of spinal fractures, which can occur even with relatively minor trauma or falls.[1][5]
The inflammation in axSpA is driven by problems with the immune system. In this autoimmune condition, the immune system becomes overactive or unregulated and begins attacking the body’s own tissues. Various inflammatory chemicals, called cytokines, play important roles in causing and maintaining inflammation. Tumor necrosis factor (TNF) and interleukin-17 are two key inflammatory chemicals involved in axSpA. Understanding these pathways has led to the development of medications that target these specific chemicals.[7][12]
Beyond the spine and joints, axSpA can affect other systems in your body. The eyes can develop inflammation, specifically uveitis, which causes redness, pain, and sensitivity to light. The digestive system may be affected, with some people developing inflammatory bowel disease or experiencing diarrhea and abdominal pain related to inflammation in the intestines.[2]
The heart and cardiovascular system can also be impacted. Although uncommon, inflammation can affect the aorta, the largest artery leading from the heart. People with axSpA have an increased risk of heart attack and stroke compared to the general population. The heart valves can also be affected in some cases.[2]
Lung complications from axSpA are rare but can occur. The chronic inflammation and changes in the rib cage can sometimes affect lung function. The constant inflammation throughout the body contributes to the overwhelming fatigue that many people with axSpA experience. This fatigue is not just ordinary tiredness but a deep exhaustion that doesn’t necessarily improve with rest.[2]
The skin may be affected through the development of psoriasis, causing red, scaly patches. The inflammatory nature of the disease means that all these different manifestations stem from the same underlying problem with the immune system, even though they may seem unrelated to each other.[1]
