The sacroiliac joint (SIJ) is often overlooked as a cause of pain, partially because it is not well visualized on standard imaging and partially because other structures may refer pain to it. This chapter reviews the anatomy of the SIJ as well as the diagnosis and differential diagnosis of SI joint dysfunction and pain, including a multitude of physical exam maneuvers such as the FABER, Gaenslen, extension, Gillet’s, sacroiliac shear, thigh thrust, compression, and distraction tests. In addition, it discusses the evidence-based approach to treat sacroiliac pain, with a focus on both conservative and nonconservative approaches such as image-guided steroid injections and radiofrequency denervation procedures and outcomes.