The SIJ is the largest diarthrodial axial joint in the body that serves as a load-transferring junction between axial spine and lower extremities. The SIJ is anatomically complex, as the joint has limited synovial characteristics in the anterior half and has a fibrocartilaginous lining with surrounding stability from various ligaments posteriorly. These rare characteristics make the SIJ vulnerable to various modes of stress. Provocative clinical tests have low sensitivity and specificity. Similarly, the unique anatomy, with oblique orientation and uneven and sigmoid shape of the joint along with variable composition from synovium to fibrous to ligamentous structures, makes imaging the joint challenging from a diagnostic standpoint. In 2013, the American Society of Interventional Pain Physicians reported in their evidence-based guidelines that good evidence exists for the diagnosis of SIJ pain utilizing controlled comparative local anesthetic blocks, fair evidence for provocative testing, and limited evidence for the diagnostic accuracy of imaging in identifying painful SIJ. Similar results were found in two different independent systematic reviews of the available literature conducted by Rupert et al and Simopoulos et al.[16,33]
However, enough evidence exists to support that the SIJ is a potential pain generator that must be considered within the differential diagnosis of low back pain, buttock pain, and radicular pain. Because of the lack of reliable clinical and radiologic tests, physicians should use a combination of provocative tests and diagnostic injections to arrive at this diagnosis. Current literature and evidence suggest that the intra-articular injection performed meticulously under fluoroscopic guidance with arthrogram may be used as a valuable tool to diagnose SIJ pain.
J Am Acad Orthop Surg. 2019;27(3):85-93. © 2019 American Academy of Orthopaedic Surgeons