An Overview of Sacroiliitis

Inflammatory Pain at the SI Joints

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Sacroiliitis is simply inflammation of the sacroiliac (SI) joint, found in your hip bone. This can lead to symptoms of pain in the lower back and buttocks.

The sacroiliac joint.

Sacroiliitis can be caused by a number of different medical conditions, including some types of inflammatory back pain. The presence or absence of chronic sarcoiliitis is a key clue in diagnosing inflammatory back pain and is often seen in axial spondyloarthritis and other rheumatic and non rheumatic disorders.


Sacroiliitis is often felt as deep pain in the low back or buttocks that gets better with activity. It might also affect the entire expanse of your lower extremity, from the groin area all the way down to your feet.

Pain from sacroiliitis tends to be worse at night or in the early morning. It is often exacerbated with standing as well. Climbing stairs, walking with large strides, and running are other weight-bearing activities that make the pain worse.

Depending on the underlying cause of your sacroiliitis, you may experience other symptoms in addition to those resulting directly from the inflammation of the SI joint.


Sacroiliitis Causes
Illustration by JR Bee, Verywell

There are a number of different causes of sacroiliitis. These include:

  • Inflammatory arthritis (such as ankylosing spondylitis)
  • Osteoarthritis
  • Injury to the joint from trauma
  • Infection

Pregnancy may also temporarily cause inflammation of the joint, because of the added weight on your back.

Sometimes sacroiliitis results from inflammatory back pain from a group of related disorders known as spondyloarthritis (also known as spondyloarthropathy). These related conditions appear to result from a combination of genetic-environmental causes. Ankylosing Spondylitis is a type of spondyloarthropathy.

For example, people with variations of certain genes are more likely to get a form of spondyloarthropathy which causes sacroiliitis.


A combination of imaging and lab tests can help with diagnosis.

Imaging Tools

A physical exam and medical exam are important diagnostic tools and can provide many clues about the underlying issue.

To definitively assess the presence of sacroiliitis, your healthcare provider will need imaging tests such as an X-ray, MRI, or CT scan.

Those can help address the presence of sacroiliitis itself, but healthcare providers also need to diagnose the underlying cause of the sacroiliitis.

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, though, is that it can take years for evidence of the condition to become apparent.

Specialized MRIs often prove the most useful of all the diagnostic imaging options. These techniques allow healthcare providers to see the active inflammation that is responsible for bone changes (subsequently picked up by X-rays or CT). For this reason, the use of MRI has, in some cases, greatly sped up the time it takes for patients to get an accurate diagnosis of their SI joint pain. Depending on your insurance plan, you may need to have physical therapy or attest that you've tried a home exercise program before an MRI will be approved.

If a person is believed to have some form of inflammatory spondyloarthritis, the presence or absence of sacroiliitis via X-ray or CT is sometimes used to help determine the type of spondyloarthritis present. For example, people with ankylosing spondylitis usually display sacroiliitis that can be viewed by X-ray or CT (as well as MRI). People with other forms might have sacroiliitis that can only be seen with an MRI.

Laboratory Tests

Other laboratory tests are also sometimes helpful in assessing the underlying causes of sacroiliitis. These might include:

  • Tests for infection
  • The genetic test for HLA-B27 (which might indicate a form of spondyloarthritis)
  • CRP or ESR tests (which also might indicate an underlying inflammatory condition)


Treatment of sacroiliitis will vary based on the underlying cause. For example, depending on the severity of your symptoms and the underlying cause, your healthcare provider may recommend:

  • non-steroidal anti-inflammatory drugs (NSAIDs)
  • pain-relieving medications
  • muscle relaxers
  • corticosteroid injections
  • antibiotics (for an infectious cause)
  • radiofrequency denervation

If you have sacroiliitis from a spondyloarthritis such as ankylosing spondylitis, medications known as TNF-alpha blocker drugs may be of benefit. Some potential options are:

  • Enbrel (etanercept)
  • Remicade/Inflectra/Renflexis (infliximab)
  • Humira (adalimumab)

Janus kinase (JAK) inhibitors have been proven effective in the treatment of multiple forms of arthritis, including ankylosing spondylitis. Two are FDA-approved for this condition:

  • Xeljanz or Xeljanz XR (tofacitinib) 
  • Rinvoq (upadacitinib)

Physical therapy and regular exercise can also often be very helpful. In physical therapy, you'll get a tailored exercise program that includes stretching, strengthening and posture exercises.

Surgery is rarely needed for the treatment of sacroiliitis, but a joint fusion procedure can sometimes be helpful if other methods are ineffective.

A Word From Verywell

It can be frustrating to feel like pain is keeping you from the activities that you enjoy the most. Know that there are resources available to help you with your pain and keep it from getting worse over time. Don't give up! By working closely with your medical team, you will empower yourself to manage your condition in the best way possible.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  5. Ho KY, Hadi MA, Pasutharnchat K, Tan KH. Cooled radiofrequency denervation for treatment of sacroiliac joint pain: two-year results from 20 cases. J Pain Res. 2013;6:505-11. doi:10.2147/JPR.S46827.

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Additional Reading

By Anne Asher, CPT
Anne Asher, ACE-certified personal trainer, health coach, and orthopedic exercise specialist, is a back and neck pain expert.