The sacroiliac joints (SI) connect the sacrum, the triangular shaped bone at the base of the lumbar spine to the left and right iliac bones, the large bones that form your pelvis.

The SI joints have several functions

They are designed as a stable joint with limited mobility.

Movement includes

Stability of an SI joint depends primarily on the stout ligaments that cross it, but there are also bony stabilisers, static soft tissue and dynamic muscular stabilisers as well as fascia. The ligament stabilisers occur on the anterior (front) and posterior (back) of the joint and include

Interaction between the erector spinae muscles and the pelvic floor is also important for stabilising the SI joints.

The erector spinae (Spinalis, Longissimus, Iliocostalis) draw the sacrum into flexion and the muscles of the pelvic floor draw the sacrum into extension. Simultaneously engaging these muscles creates opposing forces that stabilise the joints.

It is also worth mentioning that the SI joints are synovial joints and can be affected by whole-body conditions (gout, ankylosing spondylitis) that result in joint inflammation.

What is Sacroiliac Joint Pain?

The SI joint is a major contributor to low back pain, affecting between 15-25% of low back pain sufferers.

Common Symptoms include

Possible Causes of SI Joint Pain

Too much movement (hypermobility or instability) in the SI joint can cause the pelvis to feel unstable and lead to pain, typically felt on the low back and/or hip and may radiate to the groin area.

Too Little movement (hypomobility or fixation) can cause muscle tension, pain, and inhibit mobility. Pain is typically felt on one side of the low back or buttocks, and can radiate down the back of the leg (similar to sciatic pain).

Other Possible causes of SI Joint Pain

Activities that put pressure on the sacroiliac joints include

What can you do?

SI Joint Exercises focus on stabilising and strengthening the muscles around the SI joint

You’ll be familiar with some exercises we practice in class, including


Squeezing a Studio Ball between your knees

Hip Abduction using a Resistance Loop

Basic & Advanced Bird Dog

Double Knee to Chest Stretch

Single Knee to Chest Stretch

Child’s Pose

Supine Spinal Twist