What is the SI or sacroiliac joint?
The SI joint is where the sacrum meets the ilium in the lower spine. It is located just below the waist, or beltline, on both the left and right side where the hip meets the tailbone. The sciatic nerve extends through the SI joint and buttocks. When the SI joint is unstable, it can cause low back, buttock and leg pain. The SI joint is responsible for stability in the spine and pelvis and to act as a shock absorber. It is a weight-bearing joint, responsible for transferring energy from the legs and torso when sitting, walking, standing or jumping.