What Are the Causes and Symptoms of Ankylosing Spondylitis?
When a doctor tosses out a term like ankylosing spondylitis, it causes immediate trepidation and possibly outright fear. Although the condition, which is a type of inflammatory arthritis that usually affects the spine, can cause chronic back pain and stiffness, it’s not usually life-threatening, despite the scary name.
Nonetheless, if you’re experiencing ongoing back pain that isn’t the result of an injury, you want answers so you can make the pain stop. If you also find it difficult to stand up straight and tend to hunch forward when you stand and walk, ankylosing spondylitis — pronounced ank-kih-low-sing spon-dill-eye-tiss — could be the cause of your pain. Here’s a deeper look at the most common causes, symptoms and treatments for this disorder.
What Is Ankylosing Spondylitis?
"Ankylosis" means fused bones or other hard tissue due to abnormal stiffening, while "spondylitis" refers to the inflammation of spinal bones or vertebrae. As the combined name implies, ankylosing spondylitis (AS) is an inflammatory autoimmune disease that can cause small bones in the spine to fuse over time, resulting in a dramatic loss of flexibility — sometimes even a fixed hunched-forward posture — and pain.
AS is one of the two forms of axial spondyloarthritis, which the CDC believes could affect as many as 2.7 million Americans based on the results of its U.S. National Health and Nutrition Examination Survey (NHANES). Most people who suffer from this condition experience pain, but they might not know AS is the cause of their pain. It typically starts to develop in young, active adults, who may assume the source of their discomfort — which isn’t severe in the early stages — is daily activities like working out or carrying something heavy in from the car.
Unfortunately, AS is a lifelong condition that could eventually spread to the joints of the neck and ribs or even beyond that to joints in other parts of the body. One defining feature of AS is progression to the sacroiliac (SI) joints, which connect the spine to the pelvis. This inflammation in the SI joints reduces flexibility of the spine even further and causes more pain. The severity and progression of AS varies greatly from one person to the next, with some never experiencing spinal fusion and the more serious complications that go with it.
What Causes Ankylosing Spondylitis?
Many details are known about AS, but the exact cause of the disease isn’t one of them. Medical researchers know that people with the human leukocyte antigen B27 gene (HLA-B27) are at greater risk of developing AS, but the cause isn’t as simple as possessing this genetic marker. Although more than 90% of people with AS do have this gene, the vast majority of people who carry it never develop AS.
Genetics certainly play a part, but there is clearly more to it than simply possessing a particular gene. For example, some scientists believe other genes and exposures to certain viruses or bacteria could contribute to the development of AS in people with the HLA-B27 gene, but studies have not yet provided any concrete proof for these theories.
Gender "may" play a role in risk for AS, as more men than women tend to develop the disease. However, the belief that the difference is substantial was ultimately proven to be false, casting doubt on the real magnitude of the difference in risk based on gender. Research has shown that the radiographic (X-ray) findings of AS in men tend to be worse than in women, but women with AS tend to be more symptomatic.
The average age of onset for AS is between 20 and 30 years, but the average age of diagnosis is much later, between 30 and 40 years. This may indicate that the symptoms of AS are easy to ignore at a young age and are only explored once the condition progresses and causes significant pain.
What Are the Symptoms of Ankylosing Spondylitis?
The most common symptoms of AS are pain and stiffness in the lower back, buttocks and hips, with these symptoms often more prominent in the morning after waking, during the night while sleeping, and after periods of inactivity. It's also common to experience neck pain and fatigue.
Because AS commonly affects the SI joints that connect your pelvis to the lower part of your spine (sacrum), your symptoms may also include pain in the vertebrae of your lower back, your hip and shoulder joints, and the areas where your tendons and ligaments attach to your bones. In more serious cases where the ribs are affected, it can even cause issues with breathing.
Although it seems unrelated, AS can affect the eyes by causing episodes of inflammation called acute uveitis, a condition that causes pain and increased sensitivity to light. In most cases, eye symptoms predict more severe cases of AS. It’s extremely rare, but severe cases of AS can lead to serious complications with the lungs, heart and nervous system.
Over time, symptoms of ankylosing spondylitis could improve or even completely stop before worsening again. If you notice lower back or buttock pain that is typically worse in the morning or wakes you up in the latter half of the night, you should seek medical attention to either diagnose or rule out AS. Additionally, if the pain improves with exercise but actually gets worse with rest, it could be a symptom of AS.
What Treatments Are Available for Ankylosing Spondylitis?
AS doesn’t have a cure, but various medical and physical therapies can help you minimize and manage the symptoms as well as slow the progression of the damage. Medical care for AS is typically managed by a rheumatologist and usually includes medications designed to stop your immune system from attacking itself — the cause of the inflammation — and reduce the impact of symptoms.
Every AS patient responds differently to medical treatment, so it’s important to work closely with your doctor to find the right medications and the right dosages for your body to help you manage pain and reduce symptoms. Having said that, the most effective way to manage ankylosing spondylitis is to stay active. Regular exercise can help keep your spine limber and flexible so you can stand straighter.
Regular activity may also help decrease pain, and physical therapy can take it to the next level by helping you learn how to maintain good posture, safely stretch tight muscles and strengthen your core muscles. Additionally, people who avoid smoking and effectively manage their weight often experience less severe symptoms of AS.
The sooner you are aware that you have ankylosing spondylitis, the sooner you can start managing the disease and treating it with a regimen of exercise and medication. Early diagnosis and treatment allow most people to lead productive, active lives, so don’t ignore potential symptoms of AS (or any other disease, for that matter). If you are experiencing back pain that isn’t related to an injury, then it’s time to see your doctor to discuss your symptoms, especially if you have a close relative with AS or any other autoimmune disease.
Reveille JD, Hirsch R, Dillon CF, Carroll MD, Weisman MH. "The Prevalence of HLA–B27 in the US: Data from the U.S. National Health and Nutrition Examination Survey, 2009" Arthritis Rheum. 2-12’64(5):1407-11
Dean LE, Jones GT, MacDonald AG, Downham C, Sturrock RD, Macfarlane GJ. "Global prevalence of ankylosing spondylitis" 2014;53(4):650-7
Zhu W, He X, Cheng K, Zhang L, Chen D, Wang X, Qiu G, Cao X, Weng X. "Ankylosing spondylitis: etiology, pathogenesis, and treatments" Bone Res. 2019;7:22
Rusman T, van Vollenhoven RF, van der Horst-Bruinsma IE. "Gender Differences in Axial Spondyloarthritis: Women Are Not So Lucky" Curr Rheumatol Rep. 2018;20(6):35
Li S, Rui W, Quin X, Feng W, Peirong L. "Risk factors of uveitis in ankylosing spondylitis: An observational study" Medicine. 2016;95(28):e4233