The sacrum is the triangle-shaped bone at the base of the spine. It's linked to the other pelvis bones by the two sacroiliac joints, also called SI joints. Sacroiliitis is when one or both SI joints are hurt or inflamed. It can make small movements of the low back and pelvis very painful.
This condition has been linked to other diseases. They include ankylosing spondylitis, rheumatoid arthritis, psoriasis, and Crohn’s disease or colitis. Symptoms may include pain or stiffness in the hips, low back, thighs, or buttocks. Pain occurs most often in the morning or after sitting for long periods of time. The pain may get worse when you walk. The swinging motion of the hips strains the SI joints.
Sacroiliitis is caused by many factors such as:
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Heavy lifting, especially if not done the right way.
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A severe injury, such as a fall or car accident.
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Osteoarthritis.
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Pregnancy.
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Infected joint.
This condition is hard to diagnose. It may be confused with other causes of low back pain. To confirm the diagnosis, you may be given a shot of numbing medicine in the SI joint. Treatment includes rest, physical therapy, and anti-inflammatory medicines. If another health problem is the cause, then that must also be treated. More testing may be needed if your symptoms don’t get better.
Home care
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If your health care provider has prescribed medicines, take them as directed.
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You may use over-the-counter pain medicine to control pain, unless another medicine was prescribed. If prednisone was prescribed, don’t use NSAIDs (nonsteroidal anti-inflammatory drugs) such as ibuprofen or naproxen. Talk with your provider before using this medicine if you have chronic liver or kidney disease, ever had a stomach ulcer or gastrointestinal bleeding, or take a blood thinner.
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If you were referred to physical therapy, make an appointment. Be sure to do any prescribed exercises.
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Don’t smoke. Smoking reduces blood flow to the inflamed area. This makes it harder to treat. Talk with your provider if you need help quitting.
Follow-up care
Follow up with your health care provider as advised.
If you had an X-ray or an MRI, you'll be told of any new findings that may affect your care.
When to get medical advice
Contact your health care provider right away if you have:
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Increasing low back pain.
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Inflammation of the eyes.
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A skin rash or redness.
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Weakness or numbness in one or both legs.
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Loss of bowel or bladder control.
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Numbness in the groin area.
Online Medical Reviewer: L Renee Watson MSN RN
Online Medical Reviewer: Raymond Turley Jr PA-C
Online Medical Reviewer: Thomas N Joseph MD
Date Last Reviewed: 03/01/2025
© 2000-2026 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.
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