Anatomy of the SI Joint

The sacroiliac (SI) joint connects the sacrum, which is the lowest bony segment of the spine, with the lower limbs on each side.

The SI joint transmits most of the weight loads from the upper body to the lower limbs, acting as a shock absorber, relieving forces on the spine.

The SI joint is reinforced by strong ligaments, limiting motion in the joint.

The SI joint typically has the following characteristics:

  • Reinforced by strong ligaments and muscles
  • Limited in motion
  • Transmits most of the forces of the upper body to the pelvis and legs
  • Acts as a shock absorber

si joint anatomy