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Sacroiliac (SI) Joint Injection

The sacroiliac (also called the SI) joint connects the sacrum and the iliac bone in your lower back and buttocks region. The SI joint is one of the larger joints in the body. The surface of the joint is wavy and fits together similar to the way two gears fit together. Very little motion occurs in the SI joint. The motion that does occur is a combination of sliding, tilting and rotating. When the joint becomes irritated, it can cause pain in the immediate region or it can send pain into your groin, abdomen, hip, buttock or leg.

Benefits of an SI joint Injection

This injection can help identify the source of your pain. By placing numbing medicine into the joint, the amount of immediate pain relief you experience will help confirm or deny the joint as a source of your pain. If you obtain complete relief of your main pain while the joint is numb it means this joint is most likely the cause your pain source. Even if the SI joint is not the primary source of pain, the time-release cortisone that is injected into the joint can reduce any inflammation which could provide longer-term pain relief or allow you to begin physical therapy, if recommended by your physician.

Learn more about this exam:

  • We will call you prior to your appointment to discuss specific preparation instructions, risks, medications you may be taking and your past imaging exams.
  • Make arrangements to have someone drive you to and from the office or outpatient center the day of the injection.

The SI joint injection is performed by a radiologist, a medical doctor with advanced training in interpreting medical images and performing procedures. Overall you should budget about an hour and a half from check in to completion for this exam.

  • You may be asked to change into a hospital gown.
  • You will lie on an x-ray table and the skin in the targeted area will be cleaned and then numbed with a local anesthetic similar to what a dentist uses
  • Using fluoroscopy (live x-ray) for guidance, a needle is inserted into the skin and directed toward the joint. Fluoroscopy helps increase the precision of the injection.
  • The specialized radiologist injects contrast material into the SI joint thought to be causing your pain, highlighting the space to guide the steroid injection
  • Then the radiologist slowly releases a combination of anti-inflammatory (steroid) and anesthetic (numbing) medications into the joint

The radiologist will review your images and provide your doctor with a detailed report. 20-30 minutes after the procedure, you may be asked to move your back to try to provoke your usual pain. You may be asked to report your remaining pain, (if any) and also record the relief you experience. On the day of the injection, you should not drive and should avoid any strenuous activities.

Specific recovery instructions will be given to you at the time of your appointment. 

Although complications are rare, we will review possible side effects and risks with you prior to your exam so you can ask questions and decide if this exam is right for you.


NOTE: This procedure is not performed in all of our centers. Please contact the location or region nearest you for more information or to schedule an appointment. We are happy to help answer any questions you may have!