Sacroiliac joints are the joints between your spinal column and your pelvis. Your spinal column rests on your sacrum, a shield-shaped fused bone. Your hipbone on each side is called an ilium, and the joint formed between them is the sacroiliac (SI) joint. The SI joints have limited mobility and carry most of your upper body weight. Your legs are like stilts supporting the arch of your pelvis and the sacrum is the "keystone" of that arch. Sacroiliac pain is one of the primary sources of low back pain, which may be felt across the back, into the buttocks, or down the legs.

Sacroiliac joints can be injected with local anesthetic with or without steroid medications. The occurrence of typical pain with injection, and pain relief for the several hours' duration of the local anesthetic help diagnose the SI joint as a source of pain. The steroid medication is added to give relief of pain from inflammation and works over several weeks.

Injection of the sacroiliac joint does not usually require sedation. If the decision is made to use sedation, an intravenous line (IV) will be started. You will lie on your stomach supported by pillows and will be placed on a monitor that will check your blood pressure, heart rate, and the oxygen in your blood. A radiology technologist will use a x-ray machine to locate the SI joint and the doctor will numb the injection sites with local anesthetic. You will feel pressure sensations in your back as the doctor inserts the needle, and mild discomfort while placing the needle in the correct position. The doctor will then inject local anesthetic possibly mixed with long acting steroid into the joint. X-ray dye may be used to confirm the position of the needle. One or both sides may be injected.

• There are very small risks of bleeding or infection at the injection sites.
• The procedure may make no change in your pain, make it worse, or cause residual pain.
• Rarely, reactions to the local anesthetic drugs can cause flushing, ringing in your ears, or very rarely, seizures.
• Allergic reactions to medications may cause your heart and breathing to stop, damaging your brain, heart, lungs, liver, kidneys, or may cause death.

• You may experience increased pain for 24 to 48 hours after the injections.
• Temporary numbness, tingling, or weakness in one or both legs may occur. These sensations will wear off within a few hours. If these sensations continue or worsen beyond that which is described by your doctor, call the Pain Treatment Center or the on-call doctor.

It is not possible to predict to what extent, if any, this treatment will relieve your pain. It is important to note the amount of relief you get after this procedure and the length of time the relief lasts. These injections are used not only to diagnose the SI joint as a source of pain, but may provide long lasting relief as well. Treatment may include repeat injections over a period of time or the use of radiofrequency lesioning, a technique to use heat to reduce the ability of small nerves to carry pain signals from the SI joint.