The sacroiliac joint is an underappreciated cause of low back and buttock pain. It is thought to cause at least 15% of low back pain. It is more common in the presence of trauma, pregnancy, or in certain athletes. The pelvic anatomy is complex, with the joint space being variable and irregular. The joint transmits vertical forces from the spine to the lower extremities and has a role in lumbopelvic dynamic motion. History and physical examination findings can be helpful in screening for sacroiliac joint pain, but individual provocative maneuvers have unproven validity. Fluoroscopically guided injections into the joint have been found to be helpful for diagnostic and therapeutic purposes. Conservative treatment, which also can include joint mobilization, antiinflammatory medicines, and sacroiliac joint belts, generally is effective. Surgical arthrodesis should be considered a procedure of last resort.