The last segment of the spine is the sacrum. The sacrum attaches to the large pelvic bones known as the ilium.
The joints that connect the sacrum to the ilium are called the sacroiliac joints or “SI joints.”
The integrity of the SI joint depends on strong ligaments that encase and cover the joint. These ligaments compress and stabilize the joint.
SI Joint pain can develop when these ligaments become damaged or degenerate due to age, allowing the joint to have excessive motion. This excessive motion may inflame and disrupt the joint and surrounding nerves.
Pain commonly presents in the lower back, above one or both of the Posterior Superior Iliac Spine, also known as the PSIS.
In addition to the lower back pain, symptoms may present in the buttocks and thighs. Because SI joint pain can produce sciatica-like symptoms, it is very important to include the SI joint in a comprehensive, differential diagnosis of low back pain to confirm the correct pain generator is identified.