Inclusion Criteria:  18 years and older  Low back pain caused by SIJ dysfunction lasting > 6 months:  Predominantly axial pain below the L5 vertebrae with an average daily Verbal Numercial Scale Score (VNS) >4; >50% pain relief after a fluoroscopically guided intraarticular injection of local anesthetic and steroids in the SIJ but lasting less than 3 months; Positive SLBB: > 50% pain relief for a period of 2-24 h after a mulit-site, multi-depth sacral lateral branch block according to the previously described technique, calculated from a 36-hour post block diary  Exclusion Criteria:  Pregnancy  Spinal pathology that may impede recovery such as severe spondylolisthesis at L5/S1, severe scoliosis, or lumbar fusion; Active radicular pain; Worker's compensation; Cognitive limitation or linguistic barrier making pain assessment through questionnaire impossible; Implanted pacemaker or defibrillator; Refusal.