Physical pain is a funny thing. Sometimes pain makes sense, like if we fall or get a slap of a hurl across the shins. Other times it doesn’t make sense, at least not in the conventional sense that we think about it. We intuitively understand acute pain, but less so persistent pain or chronic pain as it is commonly known. The two can be differentiated by the time scale involved. A common marker of persistent pain is that which still remains 3 to 6 months since the onset, while some clinicians will extend that somewhat arbitrary point to a year. Either way, we are dealing with pain that hangs around for longer than it should. Here is a good definition of persistent pain:
Pain that is often (but not always) elicited by an injury but worsened by factors removed from the original cause, usually lasts a long time, interferes with daily function, and is not explained by underlying pathology. Biomedical intervention is frequently sought and rarely effective(Turk & Okifuji, 2010)
The burden of persistent pain is wide-scale, estimated to affect 1.5 billion people worldwide, with studies putting the prevalence point in Ireland and the UK Ireland at one third to one half of the population. Low back pain is so ubiquitous that everyone will have either suffered personally from it or will know someone close who has. It is not, however, exclusive to the low back and can present itself anywhere in the body.
Pain is a complex topic, with a myriad of potentially contributing factors. In order to resolve persistent pain, it is important to understand what pain really is and what it is telling us.
What is pain?
Pain is fundamentally a warning signal that comes from the brain when it thinks the body tissue is in danger and requires action. If the brain decides something is unsafe, it may elicit pain, and conversely, when it thinks things are safe, it removes the pain signal. This is an incredibly useful mechanism that helps steer us out of harm’s way as we navigate through life. As an example: a five-year-old puts their hand on a burning iron; the nervous system receives a danger signal from neurons (nociceptors) in the hand; the brain decides that the scalding heat is not good and generates a pain signal so that the child knows about it, and the hand is removed. The interacting elements of attention, action, emotion, and memory, help the child to learn from the experience and avoid repeating the mistake again in future. In acute instances such as this, the nociceptive signal is well correlated with damage.
And this is how we typically understand pain, that pain = physical damage. This explanatory model of pain can be traced back to philosopher Rene Descartes, who in his 1664 Treatise of Man, theorized that pain is resolved by locating the pain fibers that are causing the problem. This led to a practice of cutting specific fibers of the body to prevent the painful signal from cascading to the brain. As absurdly oversimplified as that may seem today, it is still the prevailing paradigm in Western medicine around pain. The Descartes (Cartesian) model led to an overreliance on imaging such as X-Rays and MRI’s to ‘find the problem’.
The Cartesian model that correlates tissue issues (nociception) to pain is over 350 years old, and it’s still doctrine in medicine and various therapies. The model is false. You can have tissue injury and no pain. You can have pain and no tissue injury. For too long, practitioners and patients have sought answers to their pain by exploring the various tissues, including joints, muscles, ligaments, and more.Adriaan Louw on Therapeutic Neuroscience Education
Now, let’s fast forward to 1977, and to physician George Engel’s critique of the biomedical model. Engel argued that the biomedical model oversimplified how illness was viewed and treated and did not train doctors to assess their patients holistically. This led to the introduction of the biopsychosocial model, a multifaceted approach to healing that considers the complex interaction between biological factors, psychological factors, and social factors. It brings back the interconnectedness of mind and body to our perspective of health, and it allows us a better understanding of someone’s subjective physical suffering.
Let’s look at an example of persistent pain through the prism of both the biomedical and biopsychosocial model:
Joe has had low back pain for a couple of months, he can’t remember exactly when it started getting bad or what set it off, but now it hurts nearly every day and is severely impacting his quality of life. His physician referred him to a physio, and he has since been receiving physio treatment once a week. The physio prescribed a rehab program that includes core work, glute activation, and stretches. He would get temporary relief from the massage work, but the pain would always return after a couple of days. After ten physio sessions, he was referred for an MRI scan to see if there was anything else going on. The scan came back showing a herniated disk, and spinal misalignment. Now, the cause of the pain is clear and is treated with a combination of rest, rehab exercises to improve posture, and anti-inflammatory medication But, continuing on with Joe’s story. Three months have passed since the scan, and the pain persists. So he is sent for an epidural steroid injection to help calm it down. It does help, for a while. But soon after the pain returns, and he is referred to a spinal consultant to discuss surgical options. This is the biomedical model in action, straight out of Descartes’s 1664 textbook. On the face of it, it seems like a sensible approach, chasing down the physical cause. The only problem is it didn’t work. A year down the line, and 3 months after receiving fusion surgery, Joe’s back is still hurting. At this stage, he is whithered and has given up all hope of getting his life back. This is an example of the biomedical model grossly failing the patient, and an example that is played out every day.
Now let’s rewind and we’ll play Joe’s story again, taking a biopsychosocial approach:
Joe has had low back pain for a couple of months, he can’t remember exactly when it started getting bad or what set it off, but now it hurts nearly every day and is severely impacting his quality of life. Joe’s physician carries out some testing to check for red flags and asks him about any recent physical trauma or accidents that might have led to the symptoms (Bio). He appears to be clear of any obvious physical issues. The physician then asks Joe about things seemingly unrelated to his back. He asks him about recent stressful life events (Social), and after some consideration, Joe does mention that his small business has been under a lot of pressure lately and he’s been struggling to keep up with payments. The doc then asks Joe about his emotional response to the pressures at work (Psychological). Joe says that mostly he just keeps busy and doesn’t think about it. He explains, however, that the emotional stress does come back during quieter moments, particularly at night, which has been affecting his sleep. Joe has a tendency to be very hard on himself, and he gets caught up in a cycle of negative thoughts and worries for the future. He is also becoming increasingly worried about the back pain and how it might affect his ability to work, which feeds into this vicious cycle of thoughts.
Taking a biopsychosocial approach has given us a much clearer perspective of potentially contributing factors. We can see the inter-related nature of Joe’s symptoms, and can map out a way forward that involves processing and resolving these psycho-social stressors. There are a number of possible therapeutic strategies that can be implemented towards this. Most importantly, at this stage, Joe has a better understanding for what could be contributing to his back pain.
Crucially, he is not leaving the doctor’s office believing that he is physically broken. Belief systems play a huge role in persistent pain, and in resolving pain. This makes sense in the context of the biopsychosocial model, as the mind (psycho-social) and body (bio) are not separate entities, but one and the same (biopsychosocial). The biopsychosocial model is a mindbody approach. We will discuss the impact of belief systems and mindbody approaches to medicine in the next part of the series.
But wait, what about that MRI scan showing the bulging disk? It is often a case of false association. We have pain, we see an issue in the surrounding tissue, and we make an assumption that one is causing the other. But assumptions can be misleading. There are now reams of evidence to show that tissue injury and pain are poorly correlated. In this longitudinal analysis, researchers reviewed whether MRI findings of the lumbar spine predicted future low back pain. They found that over the course of ten years, those who suffered low back pain did not have a significantly increased prevalence of disc degeneration compared to those who did not have low back pain. Meaning that if you scan the spines of asymptomatic subjects, you will find the same levels of tissue degeneration in others who are showing symptoms. This also applies to cartilage damage seen in MRI’s of the knee, of the hip, and shoulder rotator cuff tears, or any other body tissue. As Butler and Moseley put it in their book, Explain Pain: ‘We all have worn out joint surfaces and little bony outgrowths..but most people with worn joints will never know about it’. It doesn’t mean that MRI’s are never useful, but it does mean we need to be very careful about what we read into them.
Other common assumptions that are made in the treatment of back pain include: bad posture causes back pain, poor core strength causes back pain, poor flexibility causes back pain, aging causes back pain. The evidence that they are causal factors in persistent pain is not there, thus if your treatment for pain is focused on physical/mechanical issues alone, you are in for a long ride.
Let’s imagine you are having car trouble, your Astra keeps breaking down. You don’t have a clue about cars so you bring it to the mechanics. The mechanic checks the headlights, and brake lights, makes sure the windscreen wipers are working and gives the tyres a good pump. He sends you off without opening the bonnet and checking underneath the hood. That’s what treating persistent pain based on a purely mechanical model is like. I’d be looking for a new mechanic.
If persistent pain is not about issues with the tissue, what is it about? We’ll look at that in the Part 2 of this series, and in Part 3 we’ll get to strategies we can implement to help turn down the dial on pain. For now, if you are reading this and you are suffering from persistent pain, the good news is that learning about pain itself (pain neuroscience education) helps to relieve pain.
Reading 1) https://www.optp.com/adriaan-louw-on-therapeutic-neuroscience-education 2) https://www.cpdo.net/Lederman_The_fall_of_the_postural-structural-biomechanical_model.pdf 3) https://www.painscience.com/articles/mri-and-x-ray-almost-useless-for-back-pain.php 4) https://www.physio-pedia.com/Pain_Neuroscience_Education_(PNE)