Clinicians continue to focus attention on the sacroiliac joint (SIJ) as one cause of low back pain. Considerable literature now exists to support the contention that symptoms arise from the sacroiliac region. In the last couple of decades, studies with quantitative data, often using sophisticated methods, have added to our knowledge from earlier descriptive reports of SIJ morphology and motion. The unique morphology of the SIJ, together with its location, makes study of the SIJ complex. All reported studies have limitations such as small sample size or lack of randomization or methodology. The purpose of this article is to review the literature to determine the support for current beliefs, opinions, and theories on joint morphology, life-span changes, and motion. Clinicians should provide well-documented clinical case-study series if we are to understand what occurs with treatments designed to affect the SIJ.