What Causes Sacroiliitis and Is It Serious?

What is sacroiliitis?

The causes of sacroiliitis include degenerative conditions such as spondyloarthritis, axial spondyloarthritis, osteoarthritis, or viral or bacterial infections.
The causes of sacroiliitis include degenerative conditions such as spondyloarthritis, axial spondyloarthritis, osteoarthritis, or viral or bacterial infections.

Your pelvis is composed of several different bones and joints. Like all joints, the joints in your pelvis are susceptible to inflammation and wear and tear. The sacroiliac joints (SI joints) join the bones of your pelvis (the ilium) to the lower part of your spine (the sacrum). As a joint that supports the upper and lower body, it is under a lot of stress.

When the SI joints become irritated, worn out, or inflamed, it can be quite painful. If one of your SI joints is inflamed, the pain you feel is similar to the painful conditions the lower back can create when it is injured.

There are many reasons the SI joint can become inflamed and painful. It's essential to know what they are and what can cause them so you can help your doctor diagnose and treat the condition.

Symptoms of sacroiliitis

The one symptom of sacroiliitis is pain, which can be felt in a variety of areas. Doctors often misdiagnose the condition because the symptoms it presents mimic other conditions. You might feel pain in the:

  • Legs
  • Groin
  • Hips
  • Feet
  • Lower back

Types of sacroiliitis

A variety of conditions and circumstances can cause sacroiliitis. There are many influencers of sacroiliitis, so it is broken down into three types:

  • Inflammatory
  • Degenerative
  • Pyogenic

Inflammatory sacroiliitis happens when your sacroiliac joint tissue becomes inflamed for various reasons that are not degenerative or organic. Pyogenic sacroiliitis is the joint's inflammation due to an infection. Degenerative sacroiliitis forms because a degenerative bone or joint condition caused it.

Causes of sacroiliitis

The sacroiliac joint can be irritated and become inflamed if you have degenerative conditions that are causing you to walk, run, or move differently than normal. A degenerative condition commonly seen as a cause of sacroiliitis is spondyloarthritis, or arthritis that affects the spine.

Axial spondyloarthritis can develop in the lumbar vertebrae, which can cause the vertebrae to fuse. This vertebral fusion decreases the amount of flexibility in the spine and makes the sacroiliac joint move differently, causing it to become irritated and inflamed.

Osteoarthritis, also known as wear and tear arthritis, is the most common arthritis diagnosed by doctors. As you go about your life and wear out your body, your joints and skeleton tend to wear down. The more active you are, the faster your joints wear out.

Osteoarthritis usually affects the hips (among other joints), which can cause you to move and walk differently. As with a spinal degenerative condition, your sacroiliac joint becomes inflamed and starts hurting.

Rarely, a viral or bacterial infection can cause sacroiliitis. Pyogenic sacroiliitis causes pain while breaking down bone and muscle around the area.

Pregnancy causes the sacroiliac joints to loosen and stretch to prepare for birth. The stress of childbirth, walking differently, and weight gain can cause the joint to wear or become inflamed. A traumatic injury, such as a fall or automobile accident, can also cause damage to your SI joint or other related joints and bones that might cause you to alter your gait and movements.


Nearly everyone has low back pain at some time during their life. See Answer

When to see the doctor for sacroiliitis

If you're experiencing pain in your pelvic region, hips, lower back, feet, or groin, see your doctor. Sacroiliitis is not life-threatening unless you have an infection that is causing it. If you experience any signs of infection such as fever or confusion, go to the emergency room immediately.

Diagnosing sacroiliitis

When you see your doctor for pain in the lower parts of your body, they will ask specific questions to find the areas that they need to look at. If they isolate the cause of pain in your hip and lower back area, one of the tests for inflammation of your sacroiliac joint (SI joint) is pressing on specific places on your hips and butt.

If they find tenderness or other pain during the press test, they'll order an X-ray or an MRI to look at your pelvis and see if the SI joint is inflamed. The doctor can order a CT scan for different views if the MRI and X-ray don't reveal inflammation or its cause.

Treatments for sacroiliitis

If the pain in your SI joint is from osteoarthritis or is degenerative, the doctor can prescribe pain relievers, muscle relaxers, or medicine known as tumor necrosis factor inhibitors (TNF inhibitors) to relieve sacroiliitis inflammation. You might be prescribed physical therapy for your sacroiliitis to help you get joint flexibility back and strengthen the muscles around the joint.

If non-invasive methods don't alleviate your SI joint pain, the doctor can try corticosteroid injections to reduce inflammation. Another option might be to implant an electric stimulation device into your sacrum that sends electrical signals through the joint to reduce pain. Other options might include radiofrequency denervation that disables the nerves involved in your sacroiliitis pain.

Health Solutions From Our Sponsors

American College of Rheumatology: "Spondyloarthritis."

American Journal of Roentgenology: "Unilateral Sacroiliitis: Differential Diagnosis Between Infectious Sacroiliitis and Spondyloarthritis Based on MRI Findings."

Centers for Disease Control and Prevention: "Osteoarthritis (OA)."

MayoClinic: "Sacroiliitis."

National Center for Biological Information: "A Case of Acute Pyogenic Sacroiliitis and Bacteremia Caused by Community-Acquired Methicillin-Resistant Staphylococcus aureus."

National Center for Biological Information: "Sacroiliitis."