The sacrum is the triangle-shaped bone at the base of the spine. It's linked to the other pelvis bones by the 2 sacroiliac joints, also called SI joints. Sacroiliitis is when 1 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:

  • Heavy lifting, especially if not done the right way

  • Severe injury, such as a fall or car accident

  • Osteoarthritis

  • Pregnancy

  • 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

  • If your healthcare provider has prescribed medicines, take them as directed.

  • You may use over-the-counter pain medicine to control pain, unless another medicine was prescribed. If prednisone was prescribed, don’t use NSAIDs, or 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.

  • If you were referred to physical therapy, make an appointment. Be sure to do any prescribed exercises.

  • Don’t smoke. Smoking reduces blood flow to the inflamed area. This makes it harder to treat. Talk with your doctor if you need help quitting.

Follow-up care

Follow up with your healthcare provider, or 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

Call your healthcare provider right away if any of these occur:

  • Increasing low back pain

  • Inflammation of the eyes

  • Skin rash or redness

  • Weakness or numbness in 1 or both legs

  • Loss of bowel or bladder control

  • Numbness in the groin area

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