Alan P Smith BSc(Hons) MSc(Biomedical Science) DO
Most people believe the centuries old notion that if a part of the body hurts then there must be something wrong with it, and the more it hurts the more it must be injured, inflamed, infected etc. This accords well with many everyday experiences; if you stub your toe it hurts – and the harder you stub it the more it hurts. When I started out as a therapist I shared this same ‘pathoanatomical’ belief. The perception I had of my ‘job’, in treating patients with musculoskeletal pain, was that I firstly had to identify the injured anatomy (using the tests I had been taught) such as to arrive at a ‘diagnosis’, then treat their injured body part (using the remedial skills I had been taught) such as to assist healing and bring about a resolution – and that was it basically! Sometimes this approach worked very well (in acute sports injuries for example) but other times, frustratingly, the patient’s pain experiences didn’t accord with this sort of rationale at all and whilst I gave the best treatment I could It was often without any clear understanding.
Those of us who treat patients with pain will know that the accounts they give us can often seem totally inexplicable:
- pain that spreads away from an original well localised injury, sometimes to distant sites
- pain that comes and goes
- pain that persists well beyond any reasonable tissue healing time
- pain with bizarre associations – “it only hurts when I hear an ambulance!”
- pain referred to distant target areas of the body on pressing ‘trigger points’
- pain in the absence of any discernable pathology – lots of negative tests
Plus we hear stories of people horribly injured (even having to saw off their own limbs!) who feel only mild discomfort. Then there are those with amputations who feel pain in bits of anatomy they don’t even have anymore – pain outside of their physical body! Can all this be explained?
Enter the ‘Biopsychosocial’ Model of Pain
In terms of the (now abandoned) ‘pathoanatomical’ model of pain ‘no’ it cannot. But in the world of pain neuroscience significant breakthroughs have been made in our understanding of pain mechanisms over the past twenty or thirty years and especially over the last ten years – due in no small part to new imaging techniques that allow us to look into the brains of those with pain and see what’s going on. This has overturned previously held beliefs that the nervous system plays a passive role in pain – i.e. that it merely reports what’s going on in the periphery – and seen the emergence of the ‘biopsychosocial’ model of pain which tells us that whilst sensitivity to pain takes place in injured tissue (peripheral sensitisation) it is also taking place in the central nervous system (central sensitisation) by a process similar to ‘learning’. And not only that, the brain can exert powerful control over how much pain we feel. These revelations have profound implications in pain management and the way those with musculoskeletal pain should be evaluated and treated.
As hands-on therapists we are ideally placed to use this new knowledge to our patients’ advantage, and massively increase the effectiveness of our treatments. Without it there is the real risk that we can add to our patients’ problems such that their pain can become so ‘etched’ into their central nervous system as to become chronic and potentially irreversible.
Science Ahead of General Practice
Melzack and Wall introduced the Gate theory of pain in the mid-1960’s. It flew in the face of established beliefs, and the idea that touch (e.g. rubbing) could somehow influence pain was much opposed by orthodoxy. It was not until the 70’s and 80’s – and further pain research – that acceptance began to become irrefutable.
Soon after that there was the discovery of nerves coming down from the brain that could suppress pain, and that these were largely controlled by our thoughts, but (perhaps unfortunately) not our conscious thoughts. We cannot ‘will’ our heart to beat faster but if (say) we have a near miss accident in our car it does. Our brain responds to physical and/or psychological threat (real or perceived) unconsciously, but based on past experiences, conditionings, beliefs and anxieties. The descending pain suppression circuitry, as it is called, works like this. Its’ discovery was the final nail in the coffin of the ‘pathoanatomical’ model of pain and at last there was a firm scientific basis for the efficacy of a number of (complementary? ) therapies’ in pain management; bodywork, exercise, acupuncture, electrical therapies such as TENS, and also psychological interventions such as cognitive behavioural therapy. Even ‘placebo’ could be explained, and as a result it gained respectability. Those in pain who responded to placebo treatments could no longer be labelled as ‘imagining’ their pain, as being liars, or having psychiatric problems. Their pain could be seen to be just as real as that of anyone else.
A patient with leg pain due to sciatica has their source of pain in the low back – there is nothing wrong with the leg. A person with heart trouble may experience pain in the arm – but there is nothing wrong with the arm. Trigger point referred pain is much like the latter. Pain theory is now better able to explain different referred pain mechanisms and how pain can change over time, spread, and sometimes progress to pain syndromes such as fibromyalgia.
Getting the Message Across
Acceptance of the biopsychosocial model of pain required making more than a few ‘U’ turns and it was initially met with some resistance amongst medical practitioners. But ‘U’ turns are made, and those who have been in practice a long time may remember the days when standard medical advice for any sort of physical injury was ‘bed rest’, or sometimes extended use of supports! My experience is that many people are still of this mind-set and consider the slightest pain, or discomfort, during rehab to be a bad thing and a sign that they should take more rest. My apologies to sports orientated readers, I know this doesn’t apply to you!
New scientific knowledge can take time to percolate through and be implemented within healthcare, and perhaps a lot longer to be appreciated by the general populace. Perhaps the biggest problem in this present case has been the rapid speed at which scientific knowledge of pain mechanisms has advanced in recent years. The biopsychosocial model has only lately become a part of undergraduate medical, nursing, and physiotherapy curricula, so most medics/therapists at work today were never trained in it. The need for urgent retraining over a range of medical disciplines has been recognised and is taking place.
For patients with pain problems that don’t fit the pathoanatomical model it can be a frustrating journey indeed if your healthcare professional knows only that. Those with conditions such as fibromyalgia or chronic regional pain syndromes, in particular, are still commonly misunderstood and consequently treated dismissively and with disbelief. Yet there is now in existence a mountain of scientific evidence showing that the major cause of their pain is pathological pain processing within the central nervous system and associated remodelling of parts of the cortex of the brain.
Trigger Points – Where do they fit in?
The failure of trigger points to be embraced by the medical community owes much to their ‘subjective’ nature. Clinically they can only be found by skilled palpation and patient feedback, which makes ‘objective’ research very difficult. Theories put forward as to their cause, or origin, have not always been convincing and sometimes even been contradictory, with the result that many have doubted their very existence. Added to this there has not (until recently) been a good understanding of referred pain – a defining property of trigger points. But things are changing. In the last five years new magnetic resonance and ultrasound imaging techniques have been able to visualise trigger points and the taut bands they are associated with.
Trigger points appear to be tiny areas of ‘cramp-like’ contraction within a muscle sustained by electrical ‘noise’ from nearby neuromuscular junctions and a local ‘energy crisis’ such that in the absence of ATP calcium fails to be pumped away from the myofibrils. The latter is necessary for them to separate and thus the muscle ‘knot’ to relax. This situation stimulates local pain nerves and their impulses have been shown to be powerful inducers of central nervous system sensitisation – a key player in the biopsychosocial model. A lot of recent research accords with this theory and there are calls for trigger points to be taken more seriously and be better represented in mainstream medicine.
Certainly, trigger points – and associated myofascial pain – are frequently overlooked and the problems they cause misdiagnosed as something else. For example trigger points are commonly found in the infraspinatus muscle and give a referred pain pattern typical of nerve entrapment problems of the neck. But how many doctors have knowledge of trigger points, together with the time and palpatory skills to find them? Trigger points are known to form in traumatised muscles but experts agree they are not ‘isolated phenomena’. Valerie DeLaune tells us in MW February/March that “with any pain-generating condition, trigger points will form if pain has lasted long enough.” I totally agree. Researchers are finding evidence of complex cause/effect relationships between trigger points and chronic pain syndromes.
What We Can Do
When I was studying for a Masters in Biomedical science in the late 90’s the emerging biopsychosocial model of pain was a hot topic and I have kept up with developments ever since and applied them within my clinic. As tutor at the Midlands School of Massage and Manipulative Therapy I have introduced the model and give CPD seminars/workshops to graduates to update them, discuss new diagnostic considerations, and new treatment approaches, including the use of trigger points – as appropriate to those with acute, sub-acute and chronic musculoskeletal pain. Emphasis is also placed on important psychological factors and easy to use (within an ordinary treatment session) strategies to deal with worries/anxieties/attitudes and maladaptive behavioural patterns etc. that can pose real barriers to recovery. We are well placed to add these modalities to our repertoire because we give our patients ‘time’ and create the right ambience for them to be receptive.
Pain is vital to us. It provides us with the ‘drive’ to move away from a potentially injurious and life-threatening situation, in the same way as ‘hunger’ drives us to eat. Pain also provides us with the drive to protect an injured body part whilst it heals. Perhaps less well appreciated is that pain has a proactive role in creating memories (usually aversive) to increase our chances of survival by reminding us to avoid similar life-threatening situations in the future. It thus has the power to change our central nervous system. Pain processing is a complicated business involving the spinal cord and multiple areas or centres of the brain; sensory, motor, reasoning, emotional, autonomic, attentional, modulatory, etc.
It is now known that pain processing can become pathological, telling us that parts of our body hurt more than they should, or in some chronic cases when there is nothing wrong with them at all. Pain (especially if not handled well in acute stages) can outlast a physical injury for weeks, months and even years, constantly reminding us of a problem that really belongs in the past. In other words pain can become less of a symptom and more of a disease in its own right. The patient will always assume the problem is ‘all in the tissues’ because that’s what it feels like. If we perpetuate their belief and treat them purely on that basis we will be doing them a disservice. I believe we owe it to our patients to be able to work out ‘where they’re at’ and give them an appropriate and efficient biopsychosocial treatment.
Alan Smith BSc MSc DO, is a Registered Osteopath based in Castle Donington. He is Tutor at the Midlands School of Massage & Manipulative Therapy (MSMMT)