A Sacroiliac Joint injection is an injection that is performed to diagnose and treat low back and buttock pain caused by injury or disease to the sacroiliac joint (SI joint).  If the SI joints are damaged by injury or disease, these joints can cause pain in the lower back, buttocks and sometimes legs.  This is due to the inflammation and swelling within the joint space.  The injection delivers numbing medicine and anti-inflammatory medicine into the SI Joint.  These injections are typically performed  after conservative (non-surgical) treatments have have been tried and failed.  The administration of such injections can also allow time for healing to occur in the damaged area.  If the symptoms are no longer present, further injections are not indicated.  If the SI Joint Injection provides significant but transient relief, you may be a candidate for Radiofrequency Ablation which may provide long term relief of SI Joint pain.  These injections are performed under fluoroscopic guidance (x-ray) to ensure safe delivery of medication to the intended site.