Tests and diagnosis
By Mayo Clinic staffImaging tests
- X-rays. Plain X-rays can reveal signs of damage to the sacroiliac joint.
- Computerized tomography (CT scan). CT scans combine X-ray images taken from many different angles to create cross-sectional images of internal structures.
- Magnetic resonance imaging (MRI). Using radio waves and a strong magnetic field, MRI machines produce very detailed cross-sectional images of both bone and soft tissues.
Lab tests
If your doctor suspects that you have an infection in your sacroiliac joint, he or she may want to run tests on a sample of fluid from within that joint. The sample is obtained with a needle. Because the sacroiliac joint is located so deep within the body, the doctor may use ultrasound or another imaging technique to ensure that the needle is placed correctly.
Anesthetic injections
Because low back pain can be caused by so many different types of problems, your doctor may suggest using injections of anesthesia to help pinpoint the diagnosis. For example, if an injection of numbing medicine into your sacroiliac joint stops your pain, it's likely that the problem is in your sacroiliac joint. However, the numbing medicine can leak into nearby structures, and that can reduce the reliability of this test.
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- Chang-Miller A (expert opinion). Mayo Clinic, Scottsdale/Phoenix, Ariz. May 17, 2010.
- Cohen SP, et al. Randomized placebo-controlled study evaluating lateral branch radiofrequency denervation for sacroiliac joint pain. Anesthesiology. 2008;109:279.

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