Sacroiliac Joint Fusion

The SI joint can be a significant cause of lower back pain. Clinical publications have identified the SI joint as apain generator in 15-30% of chronic lower back pain patients. 1-4 In addition, the SI joint is a pain generator in up
to 43% of patients with continued or new onset lower back pain after a lumbar fusion. 5
Pelvic pain image

The SI joint is the link between the ilium in the pelvis to the sacrum, which is the lowest part of the spine above the tailbone. 

Like any other joint in the body, the SI joint can be injured and/or undergo degeneration. When this happens,people can feel pain in their buttock and sometimes in the lower back, hips and legs. This is especially true while lifting, running, walking or even lying on the involved side.
The sacroiliac joint (SI joint) is located in the pelvis; it links the iliac bones (pelvis) to the sacrum (lowest part ofthe spine above the tailbone). It is an essential component for energy transfer between the legs and the torso.
Pelvic pain image

Excessive motion in the SI joint may inflame and disrupt the joint and surrounding nerves causing pain in the lower back, hip, groin or pelvis

It’s common for pain from the SI joint to feel like disc or lower back pain, or sometimes hip or groin pain. For this reason, SI joint disorders should always be considered in lower back, hip, and pelvic pain diagnosis.