The Sacroiliac Joint

The sacroiliac joint, although having minimal movement, can be a source of lower back pain.


We need to understand a little of its anatomy to appreciate its significance as a pain producing joint.

The sacroiliac joint (SI joint) connects the sacrum to the pelvis. The pelvis is made up of two large bones, a right and left ilium. These bones are joined together in the front by a small joint known as the symphysis pubis. In the back they connect to the sacrum by a right and left sacroiliac joint.

Together the pelvis and sacrum form a large, stable and supportive base for the spine.

The SI joint possesses very strong ligaments that hold the pelvis and sacrum together. The joint surfaces are irregular and produce an interlocking action that gives the joint great stabilization and at the same time permits needed minimal motion allowing for smooth, fluid walking and running motions.

Sacroiliac Joint-Posterior

Posterior View


Anterior View

Motion of the SI Joint

The SI joint allows for five movements:

  1. Anterior tilting of the pelvis relative to the sacrum
  2. Posterior tilting of the pelvis relative to the sacrum
  3. Anterior tilting of one side with a posterior tilting of the opposite
  4. Forward tilting of the sacrum called nutation
  5. Posterior tilting of the sacrum call counter-nutation

A Stable Joint

A perfect example of the strength of a sacroiliac joint can be seen in football players. Although subjected to excessive forces, severe injuries to the SI joint in this sport is relatively uncommon.

Throughout your body, where stability is needed motion is minimized.

Provided there exists proper alignment, a full range of motion, proper muscle and ligament strength and function the SI joints should remain fully functional and pain-free.

However, with pelvic imbalance, inadequate strength and improper motion the SI joint will be subjected to injurious stresses and will become pain expressive.

Trauma due to falls and accidents may also result in painful SI joints.

Keeping It Healthy

The health of the SI joint is maintained and promoted, like all joints, through proper alignment and regular motion as is achieved by exercising through a full range of motion. This is best achieved by daily, full stride, brisk walking.

However, if misalignment is present even walking can be a painful experience and add to inflammation and subsequent harmful and permanent degeneration.

When range of motion is compromised stress processes will cause a degenerative response that produces inflammation, joint fixation, muscular and ligament weaknesses or imbalances and joint degradation which results in pain.

Pregnancy and the SI Joint

Women during pregnancy are more prone to SI joint stress and more likely to experience SI joint problems. This is due to the added body weight, the anterior abdominal weight causing a forward pelvic tilt and hormonal changes that naturally occur to facilitate delivery during the birthing process.

Much of this added stress can be minimized with attention to correcting any spinal-pelvic misalignment, strengthening and toning muscles, maintaining proper posture, wearing the right kind of shoes and engaging in regular brisk walking throughout the pregnancy.

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For information on lower back pain in women click here.

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