Ankylosing Spondylitis
Ankylosing spondylitis is a chronic inflammatory disease that primarily affects the spine and the sacroiliac joints, where the spine connects to the pelvis. Ongoing inflammation can lead to pain, stiffness, and progressive new bone formation that may eventually fuse parts of the spine. Ankylosing spondylitis typically begins in late adolescence or early adulthood and belongs to a group of inflammatory conditions known as spondyloarthritis. Early diagnosis and modern treatment can significantly improve long-term outcomes and quality of life.
What is it?
Ankylosing spondylitis is a chronic inflammatory autoimmune-related condition that primarily affects the sacroiliac joints and spine. The inflammation occurs where ligaments, tendons, and joint capsules attach to bone, gradually leading to structural damage and abnormal bone formation.
Over time, the body’s repair process may create new bone bridges between vertebrae. This process, known as ankylosis, can progressively reduce spinal flexibility and mobility. In advanced cases, portions of the spine may fuse together, resulting in a rigid posture and limited movement.
A hallmark feature of ankylosing spondylitis is inflammatory back pain. Unlike mechanical back pain, inflammatory pain typically improves with exercise and movement while worsening with prolonged rest. Many patients notice significant morning stiffness lasting more than 30 minutes and pain that wakes them during the second half of the night.
Although the exact cause remains unknown, genetics play a major role. The HLA-B27 gene is strongly associated with ankylosing spondylitis. However, many individuals who carry HLA-B27 never develop the disease, and some patients with ankylosing spondylitis do not carry the gene.
Ankylosing spondylitis is part of the broader family of spondyloarthritis disorders, which also includes psoriatic arthritis, reactive arthritis, and inflammatory bowel disease–associated arthritis.
The disease can affect areas beyond the spine. Common extra-spinal manifestations include inflammation of the eyes (uveitis), inflammation where tendons attach to bone (enthesitis), hip and shoulder arthritis, chest wall stiffness, fatigue, and, less commonly, involvement of the heart, lungs, or gastrointestinal system.
Symptoms usually develop gradually over months or years. Early signs often include chronic pain in the lower back, buttocks, or hips that persists for more than three months. As inflammation progresses, stiffness may extend higher into the spine and limit mobility.
MRI of the sacroiliac joints is the preferred imaging test for early diagnosis because it can detect active inflammation before permanent structural changes appear on X-rays. MRI can reveal bone marrow edema and inflammatory changes that are often invisible on conventional imaging.
X-rays are commonly used to evaluate more advanced disease and may show sacroiliac joint erosion, narrowing, fusion, and the characteristic “bamboo spine” appearance seen in later stages.
CT scanning may occasionally be used for detailed evaluation of bony fusion and structural abnormalities, although MRI remains the preferred test for detecting active inflammation.
Important to Know
While there is currently no cure for ankylosing spondylitis, modern therapies can significantly reduce symptoms, control inflammation, slow disease progression, and preserve mobility.
Regular exercise is one of the most important components of treatment. Stretching, posture-focused exercises, strength training, and aerobic activity help maintain spinal flexibility and overall function.
Nonsteroidal anti-inflammatory drugs (NSAIDs) are typically the first-line medication used to reduce pain and stiffness.
For patients with persistent inflammation or progressive disease, biologic medications such as TNF inhibitors and IL-17 inhibitors can dramatically improve symptoms and reduce ongoing joint damage.
Because ankylosing spondylitis can affect multiple organ systems, ongoing monitoring for eye inflammation, cardiovascular complications, osteoporosis, and other associated conditions is an important part of long-term care.
Early diagnosis has become increasingly possible because MRI can detect inflammation years before significant structural damage develops. Earlier treatment offers the best opportunity to preserve mobility and prevent long-term complications.
Red flag symptoms include sudden severe back pain after even minor trauma, progressive weakness or numbness, gait instability, loss of bowel or bladder control, severe eye pain, vision changes, chest pain, or breathing difficulty. These symptoms require prompt medical evaluation.