Is your knee pain coming from your back?

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When extremity pain is “referred” from the spine.

Have you experienced pain somewhere in your arm or leg that doesn’t seem to improve or came on for no apparent reason?

It might be because the pain you’re experiencing is coming from your spine.

The source of pain in your extremity (hip, shoulder, elbow, knee, ankle, wrist etc) can be coming from your spine. This is called ‘referred pain’ and is actually surprisingly common! One study (see reference below) found that extremity pain of spinal source occurred 43% of cases! The prevalence varies based on the joint involved, for example, its more common in the hip than it is in the ankle.

Here’s a breakdown of the prevalence of spinal source pain based on location:

  • Hip – 71%
  • Knee – 25%
  • Ankle/foot – 29%
  • Shoulder – 47%
  • Elbow – 44%
  • Wrist/hand – 38%

And when the pain is felt between joints (like your calf or hamstring area) the likelihood of spinal source increases (approximately 80%)!

How does that work? (Gets a little bit technical in this section!)

Pain location alone is actually a fairly poor indicator of the ‘source’ of the pain. Think of how a heart attack can give you pain in your left arm or a panic attack can cause numbness in your hands – the same thing applies with musculoskeletal issues. One explanation for this is due to a process called ‘somatic referred pain’ – this is where a joint or spinal segment projects ‘danger messaging’ away from itself. The body can do this via our nervous system.

Pain is actually an output from the brain. The brain receives a bunch of inputs from our body and other contextual factors (like where we are, who we’re with, how tired or stressed we are etc). These inputs all converge in the brain and the brain makes a call on whether to create a pain response. The pain response is just one way the brain responds to protect itself from a perceived threat or danger. Sometimes the brain will produce pain in a location that is actually not the ‘source’ or primary problem area.

For example, imagine that your low back is a bit stiff and it sends those messages up to the brain (without you knowing about it!). The brain then takes that information on board (along with a bunch of other information) and decides it needs to protect you from a perceived threat so it sends out a pain response to where the perceived threat is located (it just missed the mark a little).

Pain science is a heavily researched area, the above explanation is an attempt to synthesise that to give an some understanding of this phenomenon. But things always change in science so our explanations in the future may change as new information arises.

How can you identify extremity pain of spinal source?

Another study (see below) has shown the key predictors of extremity pain of spinal source, these include:

  • Paraesthesia (this refers to abnormal sensations like: pins and needles, numbness, burning or aching type pain)
  • Worse when you’re still (for example, your knee pain feels worse when you sit down, or your elbow pain increases the longer you’re at your work desk)
  • Change in posture influences your joint pain (For example, you notice your hip pain is better when you sit up really straight and worsens when you slump down)
  • No loss of motion in the joint (when you move your knee or elbow etc there’s no stiffness present you can fully bend and straighten it)
  • Loss of motion in the spine (your neck may be stiff when you rotate it one way or your low back can’t bend backwards fully)

Having these signs doesn’t guarantee your pain is referred from the spine but it makes it more likely. To properly identify the source of your symptoms a thorough examination from a McKenzie certified physiotherapist is required. But checking these things out for yourself can be easily done at home.

Why does it matter?

A big reason why extremity pain doesn’t improve with treatment is because a spinal source has been missed. So, treatment directed at where the pain is located but not at the source is usually ineffective. It’s a bit like trying to stop the water running out of a hose by putting sticky tape over the end rather than turning it off at the tap. It might influence things in the short term but doesn’t address the root cause of the problem.

Knowing where your symptoms are coming from also empowers you to self-manage. Recurrent episodic extremity pain can often be well managed long term by maintaining good spine motion. As goes the saying – prevention is better than cure!

Those references…

-Richard Rosedale, Ravi Rastogi, Josh Kidd, Greg Lynch, Georg Supp & Shawn Robbins (2019) Author’s response to Anthony Halimi and David Poulter’s letter to the editor regarding ‘A study exploring the prevalence of extremity pain of spinal source (EXPOSS)’, Journal of Manual & Manipulative Therapy, DOI: 10.1080/10669817.2019.1676970

-Rastogi R, Rosedale R, Kidd J, Lynch G, Supp G, Robbins SM. Exploring indicators of extremity pain of spinal source as identified by Mechanical Diagnosis and Therapy (MDT): a secondary analysis of a prospective cohort study. J Man Manip Ther. 2022 Jan 25:1-8. doi: 10.1080/10669817.2022.2030625. Epub ahead of print. PMID: 35076353.

Tim Cathers

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