Ankylosing spondylitis is a chronic condition that mainly causes inflammation in the spine and in the sacroiliac joints, which connect the spine to the pelvis. It is a type of spondylarthritis, a group of related conditions that share similar features. The condition often causes chronic back pain and stiffness, but it can also involve other joints and organs. While ankylosing spondylitis can lead to serious problems if not managed, many people can control symptoms and maintain a good quality of life with proper treatment and regular exercise. A team approach to care is important for the best outcomes.

Ankylosing spondylitis is a chronic form of arthritis. It mainly affects the spine and sacroiliac joints, where inflammation can lead to pain and stiffness and, over time, to fusion of the bones in the spine, making the back less flexible. The condition can also affect other joints, such as the hips, shoulders, knees, and ankles, and sometimes causes swelling in fingers or toes.

Besides the joints, ankylosing spondylitis can involve other parts of the body. In some people, this includes gut problems such as inflammatory bowel disease (either Crohn’s disease or ulcerative colitis), skin problems such as psoriasis, or inflammation in the eyes (uveitis). Some people can experience inflammation in tendons, which can cause heel pain, chest wall pain, or elbow pain. The disease often starts gradually, with symptoms appearing before age 40.

The severity and pattern of ankylosing spondylitis can vary widely. For some people, symptoms are mild and occasional. For others, pain and stiffness are ongoing and can limit daily activities.

No one knows exactly what causes ankylosing spondylitis, but both genetic and environmental factors play a role. The majority of people with ankylosing spondylitis have a specific gene called human leukocyte antigen B27 (HLA-B27), which increases the risk of developing the disease. However, many people who carry this gene never develop the condition. The HLA-B27 gene is present in about 6% to 8% of the population in the United States.

Research also points to other genes, and possibly environmental triggers, that may contribute to the disease.

Although the immune system is involved in the inflammation seen in ankylosing spondylitis, it is not clear what starts this process. The inflammation mainly targets the places where tendons and ligaments attach to bones, leading to pain and stiffness. Over time, ongoing inflammation can cause new bone to form, which may result in the fusion of spinal bones.

Risk factors for ankylosing spondylitis include genetic, age-related, and other health-related factors. The main risk factors are:

• Having a parent, sibling, or other relative with ankylosing spondylitis
• Carrying the HLA-B27 gene, a genetic marker linked to a higher risk of ankylosing spondylitis
• Being male, as the disease is more common in men than women
• Age, as symptoms usually begin before age 45, and most people have their first signs before age 30
• Having other conditions such as psoriasis, Crohn’s disease, or ulcerative colitis

Symptoms of ankylosing spondylitis usually begin gradually and can range from mild to severe. The most common symptoms are back pain and stiffness, especially in the lower back and hips. These symptoms often worsen in the morning, at night, or after periods of inactivity, and tend to improve with movement or exercise. The pain and stiffness may also spread to other areas over time.

Other symptoms can include:

• Pain in the buttocks
• Reduced flexibility in the lower back, sometimes leading to a hunched or stooped posture
• Painful, swollen joints elsewhere in the body, such as the ankles, knees, or shoulders
• Swelling of fingers or toes (dactylitis), causing them to look like sausages
• Heel pain from plantar fasciitis or Achilles tendon inflammation
• Pain or tightness in the chest, making it hard to take deep breaths
• Fatigue, or feeling very tired, which is common in ankylosing spondylitis
• Eye inflammation, which can cause redness and pain
• Mild fever, weight loss, or loss of appetite, which are less common
• Skin rashes (psoriasis) or gut symptoms (abdominal pain, diarrhea)

Diagnosis of ankylosing spondylitis is based on a combination of medical history, physical examination, and specific tests.

Doctors review symptoms, family history, and details about the pain, such as whether it improves with exercise and whether it started before age 45. During a physical exam, doctors check for spinal flexibility, posture, joint swelling, and signs of inflammation in other areas like the eyes or skin.

To help confirm the diagnosis or rule out other conditions, doctors may order several tests:

• X-rays of the spine and pelvis, which can show changes in the sacroiliac joints and spine over time
• Magnetic resonance imaging (MRI) of the sacroiliac joints, which can detect early inflammation and joint changes before they appear on X-rays
• Blood tests for markers of inflammation, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), which may be elevated in active disease
• Testing for the HLA-B27 gene, which is linked to ankylosing spondylitis
• Tests for antinuclear antibodies (ANA), rheumatoid factor, and anti-cyclic citrullinated peptide (CCP) antibodies, which are not helpful for evaluating suspected ankylosing spondylitis but may be ordered, depending on symptoms, to rule out other types of arthritis

Treatment for ankylosing spondylitis has three goals: reducing pain and stiffness, preventing complications, and maintaining mobility. The condition cannot be cured, but many therapies can help manage symptoms and improve quality of life. Treatment plans are tailored to each person and may include:

• Non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or naproxen, which are usually the first medicines used to reduce pain and swelling
• Biologic medicines, such as tumor necrosis factor (TNF) inhibitors and interleukin-17 (IL-17) inhibitors, which control inflammation by acting on specific parts of the immune system
• Janus kinase (JAK) inhibitors, which may be an option when other medicines do not help enough
• Corticosteroid injections into affected joints, which can help reduce inflammation and quickly relieve pain
• Non-biologic medicines, such as sulfasalazine or methotrexate, which may help with joint symptoms outside the spine but are not commonly used
• Physical therapy and regular exercise, which are essential for maintaining strength, flexibility, and posture. Physical therapists can create exercise plans and teach ways to ease pain and move more easily.
• Postural training and breathing exercises, which help keep the spine flexible and support lung function
• Hip replacement or other surgery, which may be considered for severe joint damage or loss of function

Complications of ankylosing spondylitis can affect the joints, spine, and other organs. The main complications include:

• Chronic pain and disability, which can limit daily activities
• Fusion of the spinal bones (ankylosis), which makes the spine rigid
• Postural changes, such as a stooped or hunched posture (kyphosis)
• Eye inflammation, which can cause vision problems if not treated
• Heart problems, including inflammation of the aorta (the body’s main artery) or abnormal heart rhythms
• Lung problems, such as scarring or reduced lung function due to limited chest movement
• Increased risk of spinal fractures, even from minor injuries
• Mood disorders, including depression or anxiety

The outlook for people with ankylosing spondylitis varies, but with proper treatment, most people remain active. Many people experience flare-ups, when symptoms get worse, and periods of remission, when symptoms improve. Severe disability is uncommon, especially with ongoing care.

Some people may develop lasting stiffness or joint damage, but regular exercise, physical therapy, and effective medicines can help maintain mobility and reduce pain.

This article was medically reviewed in October 2026.