One of the most common reasons people present to healthcare is because they are in pain. Whether it’s an ache in the shoulder that is not going away or a chronic low back problem, you probably know the frustration associated with unexplained pain. Our understanding of how pain works has come a long way in recent years: where we once thought it was a simple case of incident, leading to tissue damage, leading to pain and therefore pain equals damage, we now know pain is not always due to damage.
Let’s explore.
Perhaps a signpost in our quest to understand pain lies in a famous case study from 1995. A construction worker jumped onto a nail which pierced his sturdy work boot piercing through to the other side. He was carted off to the emergency room, pumped full of pain killers and even sedated just to get the boot off to commence treatment. To everybody’s surprise, the nail did not pierce his foot at all, in fact the nail had passed between the toes. No structural damage, not even a scratch.
So how can that be?
Pain is an output of the brain: it is our bodies way of detecting or predicting threat and is employed by the brain to encourage behaviour change to prevent harm to ourselves.
More threat equals more pain.
Many factors influence this decision in the brain and alter the perceived threat that may be present. Below is a diagram from recent research proposing all the different interlapping influencing factors of pain including individual, psychological, biomechanical, tissue injury, pain processing, behavioural, contextual and social factors. A lot more complicated than just simply tissue damage!
Think of it this way: each factor acts as an “advisor” to the brain. Some “advisors” may be louder and talk more than others and therefore have more influence on the decision of threat. In the case of a hamstring strain for example, tissue factors (including the muscle tear, inflammation, sensitivity of the muscle fibres) may be the dominant “advisor” in the initial stages while healing is occurring.
In the case of the construction worker, the tissue factors were not present. His graph may have looked something like this:
The sight of the nail passing through the work boot, anxiety about the situation, horrified faces of his co-workers, fears of not being able to go to work and maybe flashbacks to a previous foot injury that took him out of his enjoyable hobbies likely increased his perception of threat and the pain alarm bells went off. This is a great example to show how powerful these factors are in our perception of pain. This does not de-legitimize his pain experience at all, as I am sure he would be the first one to tell you. It shows us that pain is much more than just tissue damage.
An everyday example of this is a papercut: such a small and mild example of tissue damage that stings so badly! Or looking down at your leg to see a bruise (damage to the superficial blood vessels creating a bleed) that doesn’t hurt or that you don’t even remember getting.
Can I re-train my overprotective pain system?
In persistent pain, part of the problem can be this overprotective pain system: the pain experienced is not necessarily ongoing disc, nerve, muscle or ligament tissue injury. In the case of persistent pain, the way the signals from the tissues are processed is very heightened, meaning threat signals can be sent to the brain when the tissue is completely safe from damage. This can be thought of as a protective pain memory – potentially once activated for an extended time after an acute injury, the neurons become very efficient at firing. So much so, that sometimes even the thought of a painful activity can activate these neurons and cause pain!
The good news is this can be retrained. Through understanding the pain more and performing targeted exercise, we can help re-train the overprotective pain response to decrease the level of threat associated with a particular movement or task, working on desensitising the overactive areas of the pain matrix to reduce pain over time. This is not an overnight task, but the great news is that it can be re-trained, regardless of how long the pain has been present.
Pain is a very complicated, multifactorial phenomenon and is experienced very differently between individuals. A good summary of the main points of modern pain science comes from recent research amongst people with persistent pain who found these three points to be the most value when it came to understanding their pain:
This all being said, pain is complicated and the degree to which we can challenge it is highly dependent on the individual. If you have been experiencing issues with persistent pain, make sure to get a thorough assessment to get an appropriately tailored plan for your condition.
About the author
CSSM physiotherapist Hugh Feary particularly enjoys the challenge of integrating people back into sport as fast as possible. Hugh has previously worked in GP clinics and private practice as well as a variety of local sporting teams, including the Fremantle Dockers in the AFLW. Hugh’s focus is on empowering his clients with the information and tools they need to manage their own health and get back to the things they love.
References
Cholewicki J, Breen A, Popovich JM Jr, Reeves NP, Sahrmann SA, van Dillen LR, Vleeming A, Hodges PW. Can Biomechanics Research Lead to More Effective Treatment of Low Back Pain? A Point-Counterpoint Debate. J Orthop Sports Phys Ther. 2019 Jun;49(6):425-436. doi: 10.2519/jospt.2019.8825. Epub 2019 May 15. PMID: 31092123; PMCID: PMC7394249.
Leake, Hayley B.a,b,*; Moseley, G. Lorimera; Stanton, Tasha R.a; O’Hagan, Edel T.b,c; Heathcote, Lauren C.d What do patients value learning about pain? A mixed-methods survey on the relevance of target concepts after pain science education, PAIN: October 2021 – Volume 162 – Issue 10 – p 2558-2568. doi: 10.1097/j.pain.0000000000002244
Nijs J, Lluch Girbés E, Lundberg M, Malfliet A, Sterling M. Exercise therapy for chronic musculoskeletal pain: Innovation by altering pain memories. Man Ther. 2015 Feb;20(1):216-20. doi: 10.1016/j.math.2014.07.004. Epub 2014 Jul 18. PMID: 25090974.
Smith BE, Hendrick P, Bateman M, et al
Musculoskeletal pain and exercise—challenging existing paradigms and introducing new
British Journal of Sports Medicine 2019;53:907-912.
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