Sacrum

The sacroiliac joint is one of the large joints in the body and is formed by the connection of the sacrum and the right and left iliac (pelvic) bones. The sacroiliac joints have small amount of movement and transmit all the forces of the upper body to the lower body. The sacrum is the triangular-shaped bone at the bottom of the spine, below the lumbar spine. The sacroiliac joint acts as a shock-absorbing structure. Sacroiliac joint dysfunction or Sacroiliac joint pain is one of the common causes of low back pain.