Ankylosing Spondylitis
An inflammatory arthritis that primarily affects the spine and sacroiliac joints — also called axial spondyloarthritis or AS
Ankylosing spondylitis (AS) — also known as axial spondyloarthritis — is a type of inflammatory arthritis that primarily targets the spine and the sacroiliac joints where the spine meets the pelvis. Unlike mechanical back pain (which is caused by disc degeneration or muscle strain), AS is driven by immune system inflammation. Over time, chronic inflammation can cause new bone formation, leading to the fusion of spinal segments — a process called ankylosis. Early diagnosis and treatment with biologic medications can slow progression and significantly improve quality of life.
Symptoms
- Chronic low back and buttock pain that is worse in the morning or after rest (inflammatory pattern)
- Morning stiffness lasting more than 30 minutes that improves with activity
- Back pain that wakes you from sleep in the second half of the night
- Reduced spinal flexibility and difficulty bending forward
- Fatigue, a common systemic feature of inflammatory disease
- Chest pain with deep breathing (rib cage involvement in some patients)
- Eye inflammation (uveitis) — affecting approximately 25–40% of patients
- Hip and shoulder pain in more severe cases
Causes & Risk Factors
- Genetic predisposition — approximately 90% of patients carry the HLA-B27 gene variant
- Immune system dysregulation triggering chronic spinal inflammation
- Gut microbiome alterations may play a contributing role (active research area)
- Environmental triggers in genetically susceptible individuals
- Note: AS is not caused by injury or mechanical stress, unlike most other back pain
Treatment Options
Conservative (Non-Surgical)
- NSAIDs (ibuprofen, naproxen, celecoxib) — first-line treatment for pain and stiffness; some may slow radiographic progression
- Physical therapy emphasizing spinal mobility, posture, and breathing exercises
- Regular aerobic exercise — swimming and water aerobics are particularly well-tolerated
- TNF inhibitors (biologics): adalimumab, etanercept, infliximab — highly effective when NSAIDs fail
- IL-17 inhibitors: secukinumab, ixekizumab — an alternative biologic class
- JAK inhibitors (tofacitinib, upadacitinib) — newer oral options for refractory disease
- Sulfasalazine — limited spinal benefit but may help peripheral joint involvement
Surgical Options
- Spinal osteotomy — corrective procedure for severe fixed kyphotic deformity (bent-forward posture) preventing patients from looking straight ahead
- Total hip replacement — for patients with severe hip joint involvement
- In general, AS is a medical condition managed with medications; surgery is reserved for deformity correction or failed joints
When to see a spine specialist
See a rheumatologist promptly if you have had chronic low back pain lasting more than 3 months that started before age 45, is worse in the morning, improves with exercise but not rest, and is associated with buttock pain alternating sides. Early diagnosis and biologic therapy can prevent irreversible spinal fusion. See a spine surgeon if you develop severe spinal deformity or neurological symptoms.
Frequently Asked Questions
Is ankylosing spondylitis the same as inflammatory back pain?
Inflammatory back pain is a clinical pattern — morning stiffness, improvement with exercise, worse with rest — that suggests an inflammatory cause. Ankylosing spondylitis is one specific diagnosis within the axial spondyloarthritis spectrum that causes inflammatory back pain. Not all inflammatory back pain is AS, but AS always presents with an inflammatory pattern.
Does everyone with ankylosing spondylitis develop spinal fusion?
No — not all patients with AS develop significant bony fusion (ankylosis). The risk is highest in patients with elevated inflammation markers, significant sacroiliac joint involvement on imaging, and those who are inadequately treated. Early diagnosis and consistent treatment with NSAIDs and biologics substantially reduces the risk of structural progression.
What is the difference between ankylosing spondylitis and degenerative disc disease?
Degenerative disc disease is a wear-and-tear process that worsens with activity and improves with rest. Ankylosing spondylitis is an inflammatory disease that is worse in the morning and after rest, and improves with movement. Blood tests (CRP, ESR, HLA-B27) and MRI of the sacroiliac joints help differentiate the two.
Which specialist should I see for ankylosing spondylitis?
A rheumatologist is the primary specialist for diagnosing and managing AS with biologic medications. Spine surgeons (orthopedic or neurosurgeons) are consulted for severe deformity or neurological complications. Some patients also work with physiatrists or pain management specialists for additional symptom control.
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Medical disclaimer: This content is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider for diagnosis and treatment decisions. Last reviewed March 2026. ICD-10: M45.9.