The Hidden Muscle Behind Lower Back Pain | The Multifidus Explained

The image below could be one of the most important you see when it comes to having a strong, pain-free, functional back.

I know this image may not mean anything to you, but in this post, I’ll explain what you’re looking at, and why it matters more than most people realize when it comes to the health of your spine.

(If you would like to watch a short video instead of reading the blog, scroll down)

What Does This Image Show?

This is an MRI scan of the lower lumbar spine.

The darker areas you can see (circled in the image) are the multifidus muscles. Small, deep muscles that sit close to the spine. These muscles act like internal scaffolding, helping to stabilise each segment of your spine as you move.

But their role goes beyond strength.
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They are packed with sensory receptors that constantly send information to your brain about what your spine is doing. This allows your body to make small, precise adjustments to keep everything stable and controlled.

What Happens After Injury?

After a lower back injury, something important can happen: The multifidus muscles can “switch off”.

Even more importantly…

They don’t always switch back on again, even when the pain goes, and when this happens:

• The multifidus doesn’t stabilize the spine as well
• Larger muscles in the lower back have to take over
• Those muscles can become tight, overworked, and painful

​Sound familiar?

Related: Sciatica Explained: Symptoms, Treatment & Recovery Tips

The Multifidus Muscle Actually Changes

Over time, if the multifidus isn’t working properly:

• It can shrink in size (this is called atrophy)
• And it can be replaced by fatty tissue

This is exactly what you’re seeing in the image below.

As the images progress from normal → mild → moderate → severe, you’ll notice:

• Less of the dark muscle
• More of the lighter (white) fatty tissue

This is known as fatty infiltration, and the scary thing is that this can happen surprisingly fast.

A study by Hodges et al. done on pigs showed that multifidus atrophy can occur rapidly, sometimes within days of an injury, with reductions of 25% or more.

Why This Matters

​Fatty infiltration of the multifidus has been linked with:

• Lower back pain
  
• Disc degeneration
  
• Reduced spinal stability

For example, a study by Kjaer et al. (2007) found a strong association between multifidus fatty infiltration and lower back pain in over 80% of patients studied.

Why Does This Muscle Shrink?

​There are two main reasons why the multifidus muscle can atrophy:

1. Neurological Inhibition
As already mentioned, after an injury or dysfunction, the nervous system may inhibit the muscle, meaning it doesn’t activate properly.

2. Disuse
A more sedentary lifestyle can also lead to reduced activation of these deep stabilising muscles.  It makes sense that if we aren't using the muscles like they are designed, they can shrink.  This is like if you break and ankle and are in a cast for 6 weeks, your calf muscles tend to shrink or atrophy ... a lot. 

Related: How to sit with an L4/L5 or L5/S1 disc bulge

Can It Be Reversed?

This is the big question, and the answer is Yes, but it requires the right approach.

A study published in the Journal of Physical Therapy Science (2014) showed that spinal stabilisation exercises can:

• Increase the size of the multifidus
  
• Improve strength
  
• Reduce pain and disability

Another study (Journal of Radiology Case Reports, 2014) found that a combination of spinal manipulation and targeted exercises led to reduced muscle atrophy and improved function over time.

Where Chiropractic Care Fits In

Chiropractic care can play an important role in this process.  Chiropractic adjustments could help:

• Improve joint movement
• Reduce irritation in the area
• Stimulate the nervous system
• Improve recruitment of the multifidus muscles

​The facet joints in the lower spine and the multifidus muscles share the same nerve supply, so improving joint function through adjustments could help the muscles respond more effectively.

The Best Approach

The best results often come from combining:

• Hands-on care (to improve movement and reduce irritation)
• Targeted exercises (to rebuild strength and control)

​This is exactly the approach we use at Elevate Chiropractic.

Related: How to hip hinge properly: A simple technique to protect your lower back and move better

The Key Takeaway

Lower back pain isn’t always just about what hurts.

Sometimes it’s about what’s not working behind the scenes, and the multifidus could be one of those hidden pieces.
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If it’s not doing its job, your back may never feel fully stable, and you may have that low level tension and tightness and occasional twinges in the area.

Ready to Take the Next Step?

If you’ve had:

• Ongoing or recurring lower back pain
• A back injury that never felt quite right
• Stiffness or a lack of stability

It may be worth getting it assessed.

You can easily book an appointment online here and let’s figure out what’s going on and get you moving better again.

In our next blog we will show you some our favorite Multifidus strengthening exercises.

P.S. If you have any questions, feel free to contact us and we are happy to answer them for you.

References

​Faur et al. (2019). Correlation between multifidus fatty atrophy and lumbar disc degeneration in low back pain. BMC Musculoskeletal Disorders.
Kjaer et al. (2007). Are MRI-defined fat infiltrations in the multifidus muscles associated with low back pain? BMC Medicine.
Kim et al. (2014). Effects of spinal stabilization exercise… Journal of Physical Therapy Science.
Woodham et al. (2014). Long-term lumbar multifidus muscle atrophy changes… Journal of Radiology Case Reports.
Hodges et al. (2006). Rapid atrophy of the lumbar multifidus… Spine.