During my training (residency and fellowships), the sacro-iliac joint (SI joint) was rarely addressed. This complicated piece of anatomy is responsible for transferring weight from the legs to back/ torso and vice versa. The stresses across the joint can easily be 2-3 times greater than your body weight. However, this area is often ignored because we have little understanding how the SI joint can cause pain. Historically, the SI joint was thought to be the major source of leg and back pain.
Dr. Paul Saiz