What Is Sacroiliitis?

An Early Symptom of Ankylosing Spondylitis

Physical therapist explaining something to patient
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Sacroiliitis, inflammation located at the sacroiliac joints, is a key symptom of several forms of inflammatory arthritis and is often the first to make itself known in these diseases. While wear-and-tear arthritis (osteoarthritis), trauma, and pregnancy-related changes can cause sacroiliac joint pain, sacroiliitis most commonly occurs when you have chronic inflammatory arthritis in the spine, called spondylitis.

As a clinical sign, sacroiliitis plays a major role in diagnosing spondylitis.

Symptoms of Sacroiliitis

Sacroiliitis may be felt as deep pain in the back or buttocks that gets better with activity. It generally is worst at night or in the early morning. Sacroiliitis is a common cause of inflammatory back pain.

Symptoms of sacroiliitis tend to occur early on in the course of ankylosing spondylitis, and may be the reason your sacroiliac joints are tender if you have this disease. Ankylosing spondylitis is the most common type of spondylitis.

Diagnosing Sacroiliitis

To diagnose sacroiliitis, your doctor may order an x-ray, MRI or CT scan. She may also order lab tests to find out if an infection is a cause. An x-ray shows what's going on in your bones, making it a good tool for following the changes in your pelvic and spinal bones as the disease progresses.

For decades, the x-ray was the only imaging test used to diagnose sacroiliitis (and spondylitis).

The problem with using x-rays to diagnose sacroiliitis is that it takes many years for evidence of the condition to become visual. More recently, new MRI techniques have entered the scene. These techniques allow doctors to see the active inflammation responsible for the bone changes that is subsequently picked up by x-rays.

The use of MRI has in some cases greatly sped diagnosis time.

If early on, your doctor suspects spondylitis, she may order an MRI done with a specialized technique called short tau inversion recovery (acronym STIR). Another common MRI technique for sacroiliitis is the gadolinium T1 MRI. If you have the gadolinium test, you'll need to undergo a dye injection.

A CT scan may also be valuable in diagnosing spondylitis, but the specialized MRIs often prove themselves as the most useful for this purpose.

Living With Sacroiliitis

Sacroiliitis may disrupt your usual activities. For example, the pain tends to get worse when you stand for a long time, when you stand on one leg, when you climb stairs and/or when you run or walk with large strides.

Treatment for Sacroiliitis

Treatment for sacroiliitis focuses on relieving symptoms, improving function, and potentially slowing disease progression. Treatment may include pain-relieving medication, muscle relaxers, corticosteroid injections, DMARDS or TNF-alpha blockers, along with physical therapy. You'll likely learn stretching, strengthening and posture exercises in physical therapy. Procedures such as radiofrequency denervation or electrical stimulation may also help control the pain.

Surgery is rare, but sometimes the fusion of the sacroiliac joints is done to help relieve pain.


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Sacroiliitis. CHORUS Collaborative Hypertext of Radiology. Last updated: 1 September 2006.

Elyan, M. MD, Asim Khan, M., MD. Spondyloarthropathies: Update on Diagnosis and Therapy. UBM Medica. Musculoskeletal Network.

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