Ankylosing spondylitis (AS) is a chronic inflammatory disease that primarily affects the spine and sacroiliac joints, typically beginning in young adulthood. Roughly 1 in 200 American adults — close to 1 million people — meet criteria for AS or non-radiographic axial spondyloarthritis according to the Spondylitis Association of America. The disease is famously underrecognized — average time from symptom onset to diagnosis runs 8 to 11 years in many series — partly because back pain is common and inflammatory back pain is poorly distinguished from mechanical pain in primary care.
Inflammatory Back Pain: The Key Clue
Most back pain is mechanical — worse with activity, better with rest, no morning stiffness. Inflammatory back pain runs the opposite pattern. Onset before age 45, gradual development over months, morning stiffness lasting more than 30 minutes, improvement with movement, alternating buttock pain (suggesting sacroiliitis), and night pain that wakes patients in the second half of the night are classic features.
The ASAS criteria classify back pain as inflammatory when at least four of these features are present. This pattern in a young adult should trigger evaluation for spondyloarthritis rather than treatment for presumed mechanical strain. The NIAMS emphasizes that AS often begins in late teens or twenties and progresses for years before diagnosis.
Beyond the Spine
AS is part of the spondyloarthritis family and shares features with psoriatic arthritis, reactive arthritis, and IBD-associated arthritis. Peripheral joint involvement — usually large joints, asymmetric — affects about 30 percent of patients. Enthesitis at the Achilles tendon and plantar fascia is common.
Acute anterior uveitis affects roughly 30 to 40 percent of AS patients and presents as a painful, red, light-sensitive eye that requires urgent ophthalmology evaluation. Inflammatory bowel disease (Crohn’s or ulcerative colitis) affects 5 to 10 percent. Aortic root inflammation, conduction abnormalities, restrictive lung disease from chest wall involvement, and osteoporosis with vertebral fractures all occur.
Genetics and HLA-B27
HLA-B27, an MHC class I gene, is found in roughly 90 percent of AS patients but only 6 to 8 percent of the general US population. Despite this strong association, having HLA-B27 alone does not guarantee disease — only about 5 percent of HLA-B27-positive individuals develop AS. The gene is more useful as supporting evidence in someone with suggestive symptoms than as a screening test in healthy people.
Family history meaningfully raises risk. First-degree relatives of AS patients have roughly 10 to 20 times the population risk. The disease is somewhat more common and tends to be more severe in men, though under-diagnosis in women is increasingly recognized.
Diagnosis
The 2009 ASAS criteria define axial spondyloarthritis based on imaging or HLA-B27 plus clinical features. Active inflammation on MRI of the sacroiliac joints — bone marrow edema — establishes axial disease before X-ray changes appear. This category is called non-radiographic axial spondyloarthritis (nr-axSpA).
X-ray changes — sacroiliitis, vertebral squaring, syndesmophytes (bony bridges between vertebrae), and ultimately the “bamboo spine” of advanced disease — develop over years. Modern practice does not wait for X-ray findings to start treatment; that delay was responsible for much of the historical disability associated with AS.
Bloodwork shows elevated CRP and ESR in many but not all patients with active disease. HLA-B27 testing supports the diagnosis when consistent with imaging and clinical features. Per Cleveland Clinic, MRI sacroiliitis combined with at least one clinical feature is enough to classify axial spondyloarthritis even in HLA-B27-negative patients.
Treatment
NSAIDs are first-line and remain effective for many patients. Continuous NSAID use may slow radiographic progression in patients with high CRP, though gastrointestinal and cardiovascular risks limit long-term high-dose use. Naproxen 500 mg twice daily, indomethacin, and celecoxib are common choices.
For patients with persistent symptoms despite optimal NSAIDs, biologics transform outcomes. TNF inhibitors (adalimumab, etanercept, infliximab, golimumab, certolizumab) and IL-17 inhibitors (secukinumab, ixekizumab, bimekizumab) are FDA-approved for AS. JAK inhibitors (upadacitinib, tofacitinib) are alternatives. These drugs reduce pain and stiffness within weeks for many patients and can halt or slow new bone formation in the spine.
Conventional DMARDs like methotrexate and sulfasalazine are largely ineffective for axial disease but may help peripheral arthritis. Local steroid injections to sacroiliac joints, peripheral joints, or entheses help selected patients.
Exercise Is Treatment
AS is one of the few rheumatic diseases where structured exercise has a clear, durable benefit. Daily flexibility exercises, posture training, deep breathing exercises to maintain chest wall expansion, and core strengthening preserve function and reduce stiffness. Hydrotherapy (pool exercise) is particularly effective for patients with significant pain.
Yoga, swimming, and tai chi all have evidence for AS. Posture awareness — frequent reminders to stand straight, sleep on a firm mattress with a thin pillow, and avoid prolonged stooped postures — helps prevent the kyphotic deformity that long-untreated AS can produce.
When to seek emergency care: Call 911 or go to the nearest emergency room if you experience sudden severe back pain after a fall (vertebral fractures occur more easily in AS due to ankylosis and osteoporosis), new bowel or bladder dysfunction, sudden severe leg weakness or numbness, sudden severe eye pain with redness and vision changes (acute uveitis), severe chest pain, or signs of serious infection while on immunosuppressants. Vertebral fractures in fused spines can cause spinal cord injury and require immediate evaluation.
Long-Term Concerns
Cardiovascular disease is elevated, similar to other inflammatory arthritides. Aortitis and conduction blocks, while uncommon, occur in about 5 percent of patients. Restrictive lung disease from rigid chest wall reduces vital capacity in advanced disease. Apical pulmonary fibrosis is rare but classic.
Osteoporosis develops paradoxically alongside the bone formation in the spine. Vertebral fractures in AS can be missed because the spine is rigid and pain is often attributed to disease activity rather than fracture. DEXA scans are appropriate periodically.
Pregnancy in AS is generally well-tolerated, though about 30 percent of patients flare postpartum. TNF inhibitor use during pregnancy is increasingly considered acceptable based on extensive registry data, particularly certolizumab which has minimal placental transfer. Our medical conditions overview touches on chronic disease management across life stages.
When to See a Doctor
Young adults with persistent back pain — especially with morning stiffness, improvement with movement, alternating buttock pain, or a family history of spondyloarthritis or psoriasis — should be evaluated. Primary care physicians can initiate workup with HLA-B27 and inflammatory markers; rheumatology referral is appropriate for suspected disease.
Established AS patients need regular rheumatology follow-up, ophthalmology when uveitis symptoms appear, and primary care for cardiovascular risk and bone health. Many doctors recommend dental and vision care continuity given the multiple specialty needs. Comparing this disease with related axial conditions in our psoriatic arthritis guide can help patients understand the broader spondyloarthritis family.
Frequently Asked Questions
Is ankylosing spondylitis a disability?
It can be, but most patients with modern treatment maintain employment and daily function. Severe untreated disease leading to spinal fusion can produce significant disability. Earlier treatment with biologics has substantially reduced rates of severe disability compared to historical outcomes.
Can ankylosing spondylitis be cured?
There is no cure, but effective treatment can produce sustained remission and slow or halt progression. Many patients on biologics achieve low disease activity for years. Established bony fusion is permanent, which is why early treatment matters.
What is the life expectancy with ankylosing spondylitis?
Life expectancy is modestly reduced — by 1 to 5 years in older studies — primarily due to cardiovascular disease and complications of advanced disease. Modern treatment likely narrows this gap, though long-term data on biologic-treated cohorts are still maturing.
Does cracking your back help with AS?
No. Self-manipulation provides only brief relief and does not improve underlying inflammation. Aggressive chiropractic manipulation can be dangerous in advanced AS due to vertebral fragility and fracture risk. Structured physical therapy and prescribed exercise are far more effective.
What to Do Next
Anyone with chronic inflammatory-pattern back pain should be evaluated for axial spondyloarthritis. The single most consequential improvement in AS care over the past 25 years has been earlier diagnosis and earlier biologic treatment when needed. Daily exercise, posture awareness, and aggressive treatment of inflammation when active disease persists despite NSAIDs are the cornerstones of preserving long-term spinal mobility. Rheumatology follow-up plus engagement with patient communities like the Spondylitis Association produces better outcomes than navigating the disease alone.