Your spine does more than just hold you upright. It interacts with your immune, skeletal, muscular, and nervous systems. So when something goes wrong with your spine, it may have far-reaching effects throughout your body. Keeping your spine happy is an important part of your overall health.

Ankylosing spondylitis (AS) is a case in point. It’s a form of arthritis associated with long-term inflammation of the joints in the spine. The first symptoms of AS are usually pain in the low back and hips, and people often pass it off as just a “bad back.” But AS tends to get worse with time, especially if not treated. As the disease progresses, it may affect many parts of the body, including other joints and the eyes, bowels, feet, and heart.

Inflamed Spinal Joints

AS typically starts with pain in the low back and hips caused by inflammation of spinal joints there. As the years pass, inflammation—and the symptoms caused by it—may gradually move up the spine and give rise to complications.

These are three important features of AS:

  • Sacroilitis. An early hallmark of AS is inflammation of the sacroiliac joints, located where the spine meets the pelvis. This inflammation causes pain in the hips. Sometimes the pain radiates down the thighs, but never below the knees.
  • Enthesitis. Another characteristic of AS is inflammation of entheses—places where ligaments and tendons attach to bones. This type of inflammation causes much of the pain and loss of function that’s seen in the disease.
  • Fusion. The body’s repeated attempts to heal inflamed entheses can lead to the scarring of tissue, followed by the formation of extra bone. Ultimately, two or more bones of the spine may become fused, limiting flexibility in the back. In severe cases, the spine may develop a forward curvature, causing a permanently stooped posture. Fortunately, it’s far less common to reach this stage today, thanks to treatment advances.

Beyond the Spine

As time goes by, the inflammation caused by AS may affect other parts of the body as well:

  • Other joints. Inflammation may cause pain and stiffness in joints of the neck, shoulders, hips, knees, ankles, or, rarely, fingers and toes.
  • The chest. About 70 percent of people with AS develop inflammation at the junction of the ribs and spine. The point where the ribs meet the breastbone in front may also be affected, leading to chest pain. Eventually, stiffening of the ribcage may limit how much the chest can expand, reducing how much air the lungs can hold.
  • The eyes. Up to 40 percent of people with AS develop inflammation of the eye, called uveitis or iritis. This inflammation may cause eye pain and redness, sensitivity to light, and blurred vision. If not treated promptly, it can lead to vision loss.
  • The feet. Inflamed entheses may occur at the back or base of the heel. The pain and tenderness can seriously hamper a person’s ability to walk.
  • The bowels. Inflammation may cause symptoms of inflammatory bowel disease, including abdominal cramps and diarrhea, sometimes with blood or mucus in the stool.
  • The jaw. Inflammation of the jaw is uncommon, affecting no more than 15 percent of AS patients. But it can be especially troublesome, making it difficult to eat.
  • The heart. In rare cases, the body’s largest artery, called the aorta, becomes inflamed. It may enlarge so much that it distorts the shape of the valve connecting it to the heart.

Nerve Root Involvement

People with very advanced AS may develop cauda equina syndrome, a disorder affecting a bundle of nerve roots at the bottom of the spinal cord. These nerve roots transmit messages between the brain and the lower body. When damage caused by AS compresses the nerve roots, it can impair functioning of the pelvic organs or sensation and movement in the lower limbs.

Be alert for warning signs of cauda equina syndrome:

  • Problems with bladder or bowel function. You might either retain waste or be unable to hold it.
  • Severe or progressively worsening problems in the lower limbs. You may experience loss of or changes in sensation in key areas: between the legs, over the buttocks, on the backs of the legs, or in the feet and heels.
  • Pain, numbness, or weakness spreading to one or both legs. The symptoms may make you stumble when you walk.

If you develop these symptoms, it’s crucial to seek prompt medical attention. Left untreated, cauda equine syndrome can lead to impaired bladder and bowel control, sexual dysfunction, or paralysis.

What’s the Good News?

This long list of potential complications can be intimidating. However, treatment for AS may be able to prevent or delay many problems. In particular, some doctors believe that a newer group of medications called tumor necrosis factor (TNF) inhibitors may be able to change the course of the disease.