A sacroiliac (SI) joint injection – also called a sacroiliac joint block – is used to treat and or diagnose pain that may be coming from the sacroiliac joint. The sacroiliac joints lie next to the spine and connect the sacrum with the hip on both sides. There are two sacroiliac joints, one on the right and one on the left. Joint inflammation and/or dysfunction in this area can cause pain that is felt in the low back and can cause referred pain to the groin.
A diagnostic SI joint injection is used to confirm a suspected diagnosis of sacroiliac joint dysfunction. This is done by numbing the sacroiliac joint with local anesthetic (e.g. lidocaine). The injection is performed under fluoroscopy (x-ray guidance) for accuracy. Once the needle has entered the sacroiliac joint, contrast is injected into the joint to ensure proper needle placement and proper spread of medication. The numbing medication is then injected into the joint.
After the numbing medication is injected, the patient is asked to try and reproduce the pain by performing normally painful activities. If the patient experiences 75-80% pain relief for the normal duration of the anesthetic, a tentative diagnosis of SI joint dysfunction is made. A second diagnostic sacroiliac injection should be performed using a different numbing medication (e.g. Bupivicaine) in order to confirm the diagnosis.