The Sacroiliac Joint: A Common But Overlooked Source Of Low Back Pain by Sammy Mazibuko.

When someone develops low back pain, the focus is usually on the lumbar spine, discs or muscles. However, another important structure called the sacroiliac joint (SIJ) can also be a significant source of pain. Research shows that the SIJ may be responsible for 15-30% of low back pain cases, making it more common than many people realise (Kiapour et al., 2020).

Understanding how this joint works helps explain why it can become painful.

What are sacroiliac joints?

The sacroiliac joints are located at the base of the spine, where the sacrum connects to the pelvic bones. There is one joint on each side, which means you have a right SIJ and a left SIJ. The main role of this joint is, not creating movement but, to transfer load from the upper body to the legs especially during standing, walking, running and lifting. You can think of the SIJ as a force-transfer bridge between the spine and legs.

SIJ movement

Unlike the hip or spine, the SIJ is designed for stability rather than mobility. It moves a few degrees depending on the movement it is required to perform - typically around 2-4 degrees of rotation and less than 2mm of translation (Kiapour et al., 2020).

This small movement allows the pelvis to:

• Absorb shock during walking and running.

• Adjust to weight shifts when standing on one leg.

• Assist with bending, lifting and twisting.

Two subtle movements occur at the SIJ:• Nutation: the sacrum tilts slightly forward, for example when you bend forward.• Counternutation: the sacrum tilts slightly backward, for example when you lean backward during a stretch.These movements help maintain balance and allow efficient load transfer through the pelvis.

Why does such a small moving joint cause pain

Remembering that the SIJ’s role is to transfer large forces (such as body weight during walking, standing, or lifting), even small changes in its stability can cause irritation.

Pain may occur when the joint becomes:

• Too stiff – meaning it cannot absorb forces well, placing more stress on nearby structures.

• Too loose – meaning excessive movement increases strain on ligaments and surrounding muscles.

• Unevenly loaded – differences in posture, muscle strength, leg length, or previous spinal surgery can change how forces pass through the pelvis.

There are other contributing factors including injury, repeated strain, pregnancy-related ligament laxity, inflammation or conditions affecting posture and gait.

What can physiotherapists do for this hardly mobile joint?

Recognising SIJ as a potential contributor allows for more targeted treatment which often includes improving:

• Pelvic stability

• Muscle strength

• Movement control

• Load distribution

If you need treatment, please contact Debbie Cameron Physiotherapy on 031 765 88 98 to book an appointment at our Meyrickton Park or Hillcrest Medical Centre Practices. We would love to support you with managing this condition.

 References

Kiapour, A., Joukar, A., Elgafy, H., Erbulut, D. U., Agarwal, A. K., & Goel, V. K. (2020). What can physiotherapists do for this hardly mobile joint?