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Home > Sacroiliac (SI) Joint Dysfunction FAQ

Sacroiliac (SI) Joint Dysfunction FAQ

Mark W. McFarland, MD

Mark W. McFarland, DO

This three-part FAQ will provide detailed information on sacroiliac joint dysfunction and answer frequently asked questions about this condition, its causes, symptoms, diagnosis and available treatments.

Where are the Sacroiliac joints?

If you look at the human body from the front, the pelvis is the large bony structure that connects to the lower spine in the middle of the body.  The sacroiliac joints are joints that run down the length of both sides of the sacrum.  See the illustration below.

What function do the Sacroiliac joints serve in the body?

They specifically help to support the weight of the upper body while standing and they also help to transfer energy from the legs to the torso, like a super shock absorber. The SI joints may be small but are mighty as they are strengthened with many ligaments. They move frequently, but in tiny movements, equating to millimeters. They move more in women, than in men, to allow for childbirth.

What causes the SI joint to become painful? Who is most affected by Sacroiliac joint dysfunction?

As with any joint, cartilage can erode and wear away over time, causing the joint to become arthritic and painful with movement.  If SI joints move too much or too little, pain can result.  Here are some other reasons for SI joint pain:

  • Injury (sports, falls, car accidents)
  • Arthritis
  • Pregnancy
  • Infection
  • Older age stiffness
  • Leg length discrepancy

Patients who have had lower back surgeries, such as lumbar spine fusions, may sometimes experience SI joint pain. When spine vertebrae are fused together during surgery, they no longer move because they are held in place by rods and screws. Eventually, bone will form a bridge across the vertebral segments creating a fusion or bone union. As a result, adjacent vertebral segments and nearby joints will work harder when the spine needs to move to take over the workload for the surgically fused joint. Occasionally, this can cause irritation to the SI joint.

In the next segment of this FAQ, I’ll answer questions about SI joint dysfunction symptoms, diagnosis and conservative treatment.


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