This project involves the assessment of the efficacy of two different image guided techniques in patients with low back pain due to arthritis of the sacroiliac joint (SIJ). Intra-articular injection of local anesthetics and steroids is performed to relieve pain originating from the SIJ. Fluoroscopy has been used traditionally for image guidance for this procedure but there is a growing interest in use of ultrasound (US) for this procedure. US avoids radiation exposure to the patient and the health care team (HCT) and is less expensive. We aim to compare procedural efficacy related outcomes for SIJ injections performed using these image-guided modalities.