Ankylosing Spondylitis
Also known as: Axial Spondyloarthritis, AS
A chronic inflammatory arthritis primarily affecting the spine and sacroiliac joints. Causes progressive stiffness and pain. Treated with biologics and exercise.
Key Facts
- Typically begins before age 45, often in the late teens or twenties
- Men are affected 2-3 times more often than women
- HLA-B27 gene is present in about 90% of patients
- Back pain that improves with activity is a key distinguishing feature
- Early treatment before spinal fusion preserves mobility
What is ankylosing spondylitis?
Ankylosing spondylitis (AS) is a chronic inflammatory arthritis that primarily affects the spine and sacroiliac joints (where the spine meets the pelvis). Over time, inflammation can lead to new bone formation in the spine, potentially causing vertebrae to fuse and resulting in reduced flexibility.
AS falls under the broader category of axial spondyloarthritis, which includes patients with inflammatory back pain and sacroiliac joint involvement who may not yet show fusion on X-ray (non-radiographic axial spondyloarthritis).
Symptoms
- Chronic lower back pain, typically starting before age 45
- Back pain that improves with activity and worsens with rest (the opposite of mechanical back pain)
- Morning stiffness lasting longer than 30 minutes
- Pain and stiffness in the sacroiliac joints (buttock area)
- Reduced spinal mobility over time
- Peripheral joint involvement — hips, shoulders, knees
- Enthesitis — inflammation where tendons attach to bone (Achilles, plantar fascia)
- Eye inflammation (uveitis/iritis) — red, painful eye requiring urgent ophthalmologic care
- Fatigue
How we diagnose it
- Clinical history — Inflammatory back pain pattern, age of onset, family history
- Physical exam — Spinal mobility assessment, sacroiliac joint tenderness
- Imaging — MRI of sacroiliac joints to detect early inflammation; X-rays may show sacroiliitis or spinal fusion in established disease
- Blood work — HLA-B27 testing (positive in many but not all patients), inflammatory markers
- Musculoskeletal ultrasound — Useful for evaluating peripheral joint involvement and enthesitis
How we treat it
- NSAIDs — First-line therapy and often highly effective for symptom control
- Biologic therapies — TNF inhibitors and IL-17 inhibitors (such as Cosentyx) for patients who don't respond to NSAIDs. Some are available as infusions in our on-site infusion center.
- JAK inhibitors — Newer oral targeted therapies
- Physical therapy and exercise — Critical for maintaining spinal mobility and posture; this is not optional
- Monitoring — Regular clinical assessment, inflammatory markers, and periodic imaging to track disease progression
At Synergy Rheumatology
Early diagnosis of AS changes outcomes — starting treatment before spinal fusion occurs preserves mobility. We use ultrasound to evaluate peripheral enthesitis and joint involvement. When biologic infusions are needed, they're administered on-site. Active clinical trials may offer access to emerging therapies for AS.
Have questions about ankylosing spondylitis?
Schedule an appointment to discuss your symptoms, diagnosis, or treatment options with Dr. Fellows.