What is pain?

One of many commonly accepted definitions of pain is ‘an unpleasant sensory and emotional experience that is resultant from many factors including;

         - potential or actual tissue threat or damage

         - previous experiences

         - other sensory inputs’

         (Treede, 2018).

 As our understanding of the multiple factors influencing pain has developed, we now understand that pain is influenced by not only potential or actual tissue damage but also our previous experiences and knowledge, and other sensory input, like what we see, hear, taste, smell, feel.

Whilst the definition above includes some of the major components of pain, perhaps the most important word in this definition is experience.

Experiences are completely subjective, and pain is no different - which is why it is impossible to ‘pigeon hole’ pain. In line with our definition of pain, there are many examples where tissue damage isn’t required to experience pain but never the less, that pain is still very real.

 

Potential or actual tissue threat or damage

A famous case study of the pain experience involved a builder in 1995 who, having jumped down on a 15cm nail, presented to the emergency department. He was in excruciating pain, needing to be sedated with fentanyl and midazolam (a strong opioid and muscle relaxant).  However, when his boot was removed, it was discovered the nail had, in fact, penetrated between the toes: the foot was entirely uninjured (Fisher, Hassan & Connor, 1995).

(Fisher, Hassan & Connor, 1995).

(Fisher, Hassan & Connor, 1995).

In this case, tissue damage had not taken place and yet the builder suffered as though in excruciating pain. The brain had perceived that tissue damage had occurred and an experience of pain followed. This incredible story has been one of the forefronts of changing our previous beliefs that tissue damage is necessary for pain to be experienced. This case study also gave rise to the idea that pain depends on the amount of threat to our tissue and existential existence, and thus if there is sufficient threat to our body, pain will likely emerge to ensure we take action and protect ourselves. In this example, the action that the pain motivates is to get help, stop moving, and call emergency services.

Previous Experiences

Unsurprisingly, a previous experience of pain can influence future pain experiences. A common narrative is ‘I rolled my ankle and it hurt exactly like it did when I injured it years ago, but when I went to walk it actually felt ok’. Sometimes it can feel like the body remembers pain and reproduces it even if the same injury hasn’t occurred

When the builder landed on the nail his brain would have tapped into his previous experiences of what he knows about nails going through boots (it hurts), perhaps he’s heard stories of similar injuries, perhaps he’d had an injury before where he had to take time off work for a foot injury and so there was further threat beyond the tissue damage.

Based on this knowledge his brain is predicting the consequences and threat associated with the potential injury, and his previous experience has determined a large amount of threat. Pain in this instance has been a protective, adaptive experience.

Other sensory inputs

If we return to the story of the builder in 1995, his story is an excellent example of other sensory inputs informing pain. His brain would have used the visual input of a nail piercing through both sides of his foot and perhaps also the feeling of the nail puncturing the boot. Through its processing, it would have determined that a threat was present, and hence pain without any actual damage was experienced.

The brain constantly uses sensory inputs to tell us about the environment we’re in. We know that when we see a red colour when experiencing an unpleasant cold stimulus (-20deg) we perceive more pain and a hot sensation than if a blue light is shown (Moseley and Arntz, 2007). Similarly, if we hear a creaky door noise at the same time we have pressure applied to our back we perceive more pressure and stiffness than if we hear a gently wooshing noise (Stanton, 2017). This suggests that we are using this information all the time to determine the amount of threat in our environment.

What’s in your cup?

After breaking down the definition of pain, we can see that the traditional beliefs of tissue always needing to be physically compromised to cause pain is flawed. So why does pain happen?

Greg Lehman, a fellow clinician, has a helpful way of breaking down factors that can lead to the pain experience. Lehman uses the analogy of a cup, and in the cup, all the factors that can lead to or amplify the experience of pain.  He explains that factors such as poor sleep, unhelpful beliefs, worry, stress, fear as well as tissue health can ‘fill your cup’. When the cup overflows an experience of pain occurs. You’ll note that tissue health is acknowledged in this analogy, but that it’s one of many factors.  

("Tissue changes and pain: explaining their relevance", 2019)

("Tissue changes and pain: explaining their relevance", 2019)

Pain may not be the most reliable experience to indicate as to what’s occurring in the body but I’ve always personally found it to be comforting to look at it as the body’s way of protecting itself.

Perhaps pain isn’t something we need to define or explain but rather an experience we should acknowledge and respect as part of being a human being. If you are dealing with pain, there may be many factors at play influencing your experience. This becomes important to acknowledge as everyone’s experience is unique and there are many strategies that can be hugely beneficial in your journey that lies beyond a quick-fix surgery or a silver bullet treatment.

End note: It’s important to note that pain is vastly complex and so if it’s causing you stress, worry and fear consulting a health care professional is advised.

 

 

References

Fisher JP, Hassan DT, O’Connor N. Minerva. BMJ. (1995); 310:70.

Moseley, L. G., & Arntz, A. (2007). The context of a noxious stimulus affects the pain it evokes. PAIN, 133(1), 64-71. doi: 10.1016/j.pain.2007.03.002

Stanton, T. R., Moseley, G. L., Wong, A., & Kawchuk, G. N. (2017). Feeling stiffness in the back: a protective perceptual inference in chronic back pain. Scientific reports7(1), 9681. doi:10.1038/s41598-017-09429-1

Tissue changes and pain: explaining their relevance. (2019). Retrieved 11 August 2019, from http://www.greglehman.ca/blog/2017/3/6/tissue-changes-and-pain-explaining-their-relevance

Treede R. D. (2018). The International Association for the Study of Pain definition of pain: as valid in 2018 as in 1979, but in need of regularly updated footnotes. Pain reports3(2), e643. doi:10.1097/PR9.0000000000000643