What Are The Symptoms of AS?

Reviewed by: HU Medical Review Board | Last reviewed: February 2019 | Last updated: February 2023

Ankylosing spondylitis (AS) is a type of spondyloarthritis and causes chronic inflammation in the joints which can lead to joint damage or fusion. It mainly affects the joints in the spine (between the vertebrae), although it can also affect other joints in the body. Some people also experience extra-articular manifestations, symptoms that affect other parts of the body.1

image of columns of spine

Symptoms of ankylosing spondylitis

Most people with AS begin to have symptoms as teens or young adults, although some people have symptoms start earlier (in childhood) or later in their adult years. The most common early symptom is pain and stiffness in the low back and sacroiliac joints, also called the SI joints. The SI joints are at the very bottom of your spine. This low back pain is usually worse after periods of inactivity, such as in the morning after a night's sleep, and improves with activity. Early symptoms can also include fatigue, a mild fever, or loss of appetite.2,3

Not everyone has the same early symptoms, and marked differences have been noticed in women with AS compared to men with AS. Women with AS may be more likely to have pain and stiffness in their neck first rather than the lower back.2

illustration of curvature loss in spine

More symptoms of AS

While each individual with AS can have their own unique set of symptoms and there is a wide variation in the rate and pattern of progression, as the disease progresses, the chronic inflammation wears away at the bone tissue and the body's response of rebuilding the bone can lead to fused joints. New bony tissue can also encompass where the ligaments attach to the joint. The calcification of the spinal ligaments is called syndesmophytes.4

AS can progress up the spine from the sacroiliac joints to other vertebrae in the chest and neck. Inflammation or fusion of the joints between the ribs and spine or between the ribs and the breastbone can make it difficult to fully expand the chest cavity, causing chest pain or difficulty taking deep breaths.5

image of pelvic skeletal anatomy

AS can also cause inflammation in the locations where the ligaments and tendons attach to the bone (entheses). This inflammation is called enthesitis and can cause "hot spots" of tenderness along the spine or along the back of the heel.2,3

AS may also affect the joints in the periphery of the body, called peripheral AS. The hips, knees, or shoulders may also become inflamed, painful, and stiff. Some people develop inflammation in their fingers or toes, which can cause a sausage-like swelling called dactylitis.6

Extra-articular symptoms

Extra-articular symptoms of AS include those which are beyond the joints. The chronic inflammation caused by AS can also cause symptoms in the eyes (uveitis), bowels, or lungs. Uveitis is the most common extra-articular manifestation of AS, occurring in about 25 to 30 percent of people with the disease. Uveitis can cause eye pain, redness, blurry vision, sensitivity to light (photophobia), and increased tear production.7

An estimated 5% and 10% of people with AS have inflammatory bowel disease (IBD), such as Crohn's disease or ulcerative colitis. In addition, a much larger percentage of people with AS experience gut inflammation, which may also cause intestinal symptoms including diarrhea and abdominal pain.8

While not as common as eye or bowel inflammation, the chronic inflammation of AS can also damage the lungs, causing shortness of breath or difficulty breathing deeply.9

Delay in diagnosing AS

One of the challenges in properly diagnosing AS is that its primary symptom - low back pain - is a common condition among the general public and can be caused by several other conditions or circumstances. Early symptoms such as joint pain may not be accompanied by visible changes on x-rays, and some doctors may fail to recognize early stages of AS. Studies have found that people with AS experience an average of 8-11 years between the onset of symptoms and a diagnosis. However, early diagnosis and proper treatment are important to delay or stop the progression of the disease and maintain quality of life and mobility.10