There is a relatively high incidence of sacroiliac joint (SIJ) pain and dysfunction among patients undergoing evaluation for low back pain. Low back pain is a leading cause of disability globally. SIJ dysfunction can affect people of varying age ranges, with a higher distribution in several clusters, including pregnant women and adults who have undergone lumbar or lumbosacral fusion surgery. SIJ pain or dysfunction is estimated to account for 15% to 30% of all cases of axial low back pain and is an often underrecognized and undertreated cause of chronic low back pain. This chapter will provide information on the physiologic, psychologic, and physical effects of SIJ pain and how those factors impact the personal, societal, and global burden of disability from SIJ pain. Tools for the evaluation of disability are briefly discussed.