 The effectiveness of ultrasound-guided sensory blocks and RFA will be directly compared to the effectiveness of fluoroscopic-guided sensory blocks and RFA. In patients who have had the SIJ RFA procedure previously, their current ultrasound-guided PDQQ-S scores will be compared to their previous fluoroscopic-guided PDQQ-S results. In patients who are receiving the SIJ RFA procedure for the first time, a database of SIJ RFA PDQQ-S scores of patients treated over the past 5 years with the fluoroscopic-guided RFA technique is available for comparison. Their results will be compared to age and pre-RFA matched patients from the database. 