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Ankylosing Spondylitis

What Is Ankylosing Spondylitis?

Monday, April 15, 2013 - 12:36
Contributors to this article: 

H. Ralph Schumacher, Jr MD
Guy Slowik FRCS

Ankylosing spondylitis is a form of arthritis that primarily affects the spine. Spondylitis is an inflammation of the vertebrae, which are the building blocks of the spine.

  • Spondylos is the Greek word for vertebra
  • Ankylosing, from another Greek word, agkylosis, means causing stiffness and immobility of a joint

Inflammation is the body's response to a variety of causes of irritation or injury. In this disease, the inflammation causes:

  • Swelling
  • Stiffness in the joint between the pelvic bones (the ilium) and the wedge-shaped bone at the base of the spine (the sacrum)
  • Pain
  • Difficulty moving

Ankylosing spondylitis also can cause inflammation of the eyes, lungs, and heart valves.

Here is how ankylosing spondylitis progresses in the body:

  • Ankylosing spondylitis causes inflammation of the ligaments and tendons where they connect the vertebrae.
  • This inflammation causes some damage to the bone, and the body heals this damage by growing new bone.
  • This bony growth replaces the elastic soft tissue and can fuse the joints of the vertebrae.
  • This fusion causes further stiffness and pain.
  • Stiffness and pain usually begins in the pelvis and near the base of the spine and progresses upward through the back to the neck.
  • It can also affect the hips and shoulders, the other larger joints of the arms and legs, and the heels.

Ankylosing spondylitis is a relatively uncommon disease that usually strikes in the late teens and early adulthood. It can be mild or somewhat severe. Early diagnosis and treatment can control the pain and stiffness and reduce the possibility of major disability.

Nice To Know:

Ankylosing spondylitis is one of a group of arthritic diseases called "spondyloarthropathies." These diseases, which tend to cause chronic inflammation of the spine, include:

  • Reactive arthritis, formerly called Reiter's syndrome, an arthritic disorder that often affects several joints in the legs such as knees, the feet, ankles, and sacroiliac joint following a triggering intestinal or genital infection.
  • Psoriatic arthritis a form of arthritis associated with scaly skin lesions (psoriasis), especially on the fingers and toes.
  • Arthritis associated with inflammatory bowel disease (Crohn's disease).
  • Arthritis associated with ulcerative colitis.

For further information about Crohn's disease, see Crohn's Disease.

For further information about ulcerative colitis, see Ulcerative Colitis.

Understanding The Spine

The spine is made up of 33 bones called vertebrae and 110 joints. It is divided into:

  • Seven cervical vertebrae (neck)
  • 12 thoracic vertebrae (the upper back with the attached ribs)
  • Five lumbar vertebrae (the lower back)
  • Five sacral vertebrae (that fuse to form the sacrum)
  • Four coccygeal vertebrae (the tailbone)

The neck is the most mobile area of the spine. The flat, triangular sacrum is joined to the pelvis by two sacroiliac joints. The ilium is the broad, wing-like plate of the pelvis.

Each of the joints is held together by tendons and ligaments and separated by intervertebral disks.

Facts about ankylosing spondylitis

  • A tendency to develop ankylosing spondylitis runs in families; it is 10 to 20 times more common in people whose parents or siblings have it.
  • It is most prevalent among Native Americans, some Asians (but not Japanese), and white Europeans.
  • Ankylosing spondylitis is a relatively uncommon disease. According to the American College of Rheumatology, 129 out of 100,000 people in the United States have ankylosing spondylitis.
  • As many as two million Americans are living with ankylosing spondylitis.
  • Ankylosing spondylitis occurs in men three or four times more often than in women.
  • It most often begins between the ages of 20 and 40, but in some cases it may begin before age 10.


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