Subjects with pain suspected to be generated by one SI joint will undergo three diagnostic SI joint blocks each separated by one week. Two blocks will be with local anesthetic (LA) and one will be a sham block (SB). Both the Coordinator (collecting pain assessments) and subject will be blinded to the sequence of blocks (LA or SB each time). The sequence of blocks will be randomly assigned for each subject on study. The subject's participation in the study is complete after 6-month post-procedure assessment.