where is the si joints on a skeleton
Human Anatomy Â» Body Systems Â» Skeletal System Â» Sacroiliac Joint. Sacroiliac joint is a synovial joint between sacrum and ilium of the pelvis. The articulating surfaces are kept together by strong ligaments. In humans, the sacrum supports the vertebral column and is in turn supported by an ilium on each side. The articulating surfaces are flat in infants and irregular in adults.