SI Joint Pain Isn’t About “Alignment” — It’s About How Your Body Handles Force

If you’ve ever been told your pelvis is “out of alignment,” your SI joint is “rotated,” or something needs to be “put back into place,” you’re hearing one of the most common explanations for low back and pelvic issues.

It sounds logical — but it’s not how the body actually works.

To understand why, we need to look at how the sacrum and pelvis are actually designed to handle load.

Pelvic Floor Therapy in Glastonbury, CT

Understanding SI Joint Pain: Anatomy, Load Transfer, and Stability

At the center of this system is the sacrum — a triangular bone at the base of your spine that connects your upper body to your lower body. On either side are the sacroiliac (SI) joints. These joints are not built for large movement. Their primary role is force transfer.

Every time you stand, walk, or lift, force moves:

Spine → Sacrum → SI joints → Pelvis → Legs

Here’s the critical piece:

The orientation of the SI joints creates shear forces, which are inherently destabilizing. Without a system to control those forces, the pelvis would not remain stable under load.

Pelvis view illustrating the sacrum articulating with the ilia at the sacroiliac (SI) joints — key load-transfer interfaces between the spine and lower extremities.

Stability Is About Force, Not Position

The body stabilizes joints through two systems:

• Passive stability → ligaments and joint shape

• Active stability → muscle-driven compression

Passive structures provide baseline support, but they are not sufficient under dynamic load.

Real stability comes from force closure — coordinated muscular compression across the joint. This is where the “alignment” model breaks down.

The SI joint does not need to be “put back into place.”It needs to be properly loaded and stabilized.

The Core and Pelvic Floor: The System Most People Miss

The “core” is not just your abs — it’s a pressure system:

• The transversus abdominis provides circumferential tension

• The diaphragm regulates pressure from above

• The pelvic floor supports from below

Together, they create a controlled pressure environment that stabilizes the spine and pelvis.

If this system is not functioning well, force distribution becomes inefficient — and other muscles begin to compensate.

Comparison of male and female perineal musculature highlighting key structures involved in continence, sexual function, and pelvic floor support. Image by OpenStax (CC BY 4.0).

What the Research Actually Shows

Pel et al. (2008) analyzed SI joint mechanics using a 3D biomechanical model.

Key findings:

• Baseline SI joint shear forces reached ~563 N per side

• Larger muscles increased compression by ~70%

• True stability required ~400% increase in compression

Most importantly:

Stability was achieved when activation shifted to:

• Transversus abdominis

• Pelvic floor muscles

This created a “clamping” effect across the SI joint, significantly improving stability.

Anterior lumbar and pelvic musculature including QL, psoas major, and iliacus. Source: OpenStax (CC BY 3.0).

Why This Changes How We Treat SI Joint Pain

If SI joint pain is a force management issue, then treatment needs to reflect that.

Manual therapy can reduce symptoms, but it doesn’t fully solve the problem on its own.

Long-term improvement comes from:

• Restoring pressure control

• Integrating pelvic floor function

• Improving how load moves through the body

A Better Approach to SI Joint Pain

At Bray Chiropractic & Wellness, the goal is not to chase alignment — it’s to improve how your body handles force.

That means assessing:

• Movement patterns

• Load transfer

• Pelvic floor function

Schedule an evaluation

Frequently Asked Questions About SI Joint Pain

Is my SI joint actually out of alignment?

In most cases, no. The joint has very limited movement. Symptoms are more often related to force distribution than structural position.

Can an adjustment fix SI joint pain?

It can help short-term, but without addressing underlying mechanics, symptoms often return.

What does the pelvic floor have to do with SI joint pain?

It plays a key role in stabilizing the pelvis and controlling pressure. Without it, the SI joint is less stable under load.

Why does my pain keep coming back?

Usually, because the underlying force management system hasn’t been addressed.

References

1. Pel, J. J. M., Spoor, C. W., Pool-Goudzwaard, A. L., Hoek van Dijke, G. A., & Snijders, C. J. (2008). Biomechanical analysis of reducing sacroiliac joint shear load by optimization of pelvic muscle and ligament forces. Annals of Biomedical Engineering, 36(3), 415–424. https://doi.org/10.1007/s10439-007-9385-8