Why does it hurt?

Understanding your pain and other symptoms

We know that if you understand your pain and symptoms it helps you to deal with them more effectively. Therefore pain education is a key part of the treatment process. So we will tell you about your pain and how to apply this knowledge.

Based on the latest understanding of pain, this page will provide you with information about pain and its influences.

Here is a great article written by Lorimer Moseley about current understanding of pain in 2007:

Reconceptualising Pain 2007

The International Association for the Study of Pain (IASP) defines pain as ‘an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage’

Pain research is advancing rapidly so that we can understand and the mechanisms far better now than ever before. Our knowledge is being translated into clinical interventions that are more effective in relieving pain and restoring normal movement and function.


Pain is a device that serves to protect us. When we injure our tissues it usually hurts, although the level of pain is not related to the amount of actual damage (think paper cut – ouch, yet small injury; phantom limb pain – no limb but it hurts!). Feeling pain is the end result of very rapid assessment of the situation by the brain. Pain is a motivator to take action in order to get out of danger. There are a few people in the world who do not feel pain and this means that they have no way of determining whether there is a problem or not. Consequently pain is important for normal function and we learn from the experience from an early age – don’t touch the oven, it is hot!

So what is happening?

When you are feeling the pain of an acute injury there are many processes within the body in action, involving numerous systems. This includes the nervous system, immune system, endocrine system and musculoskeletal system, all of which respond to the need in order to promote survival. When there is a threat, the body protects itself by using these systems to get out of trouble. Pain is one of the responses and usually the one we take most notice of along with changes in the way we move, limping for example. There has been a significant focus on the nervous system and pain that has helped our understanding hugely. However, now we must think about the integrated role of all these systems and how they contribute and influence the experience of pain to provide better treatment.

When tissues are damaged chemicals (e.g./ inflammatory, immune messengers) are released that excite the nerves that detect danger (nociceptors) amongst other roles. This is the inflammatory process and is a normal part of healing. It really kick-starts the system. Pain, swelling, redness and difficulty moving are all part of inflammation and are all normal. There is debate about the use of anti-inflammatories at this point – do we really want to slow down or interrupt a natural part of healing? Nociceptors are usually quiet as they have a high threshold for activation. However, when they are sensitised by these chemicals, the threshold is lowered and they send signals to the spinal cord (dorsal horn). These signals are ‘danger’ signals and not pain signals as you will see. The arrival of these signals in the spinal cord alters its level of activity. Increased excitability develops in the spinal cord due to the release of peptides such as CGRP and SP in response to the signals from the tissues. As these signals continue to arrive from the periphery, the excitement builds.

The neurons of the spinal cord then send signals up towards the brain. They can also communicate with other levels of the spinal cord and cross to the other side (the way in which symptoms can be felt in different locations). The brain and the brain stem meanwhile can influence the excitability of the spinal cord by sending messages downwards (descending mechanisms), sometimes inhibiting and sometimes facilitating the process. There are a number of chemicals involved including serotonin, noradrenaline and natural opiates that we produce intrinsically. This is in effect how we can amplify and diminish the pain that we experience through attention, distraction, dealing with fears, stress, emotional state, beliefs and movement. Common treatments such as TENS an acupuncture are deemed to provide relief via these pathways.

In essence the brain receives danger signals and has to make sense of the situation based on what it knows from prior experiences. If there is a perceived threat, the brain will give the experience of pain as a motivator for you to take necessary and sensible action. Clearly this all happens very quickly. Of course there are also reflexive actions such as the withdrawal of the hand from a hot surface or the foot form a drawing pin. The key point is that pain is a brain experience, in other words, we feel pain when the brain determines there to be a danger to us. If there is something that is more important such as escaping from a burning building, the brain can use the descending mechanisms to block the danger signals and thereby allow for appropriate evasive action.


When the danger has passed and healing is progressing, the sensitivity usually decreases as the neuron thresholds for firing a restored. Soft tissues do take a number of weeks to heal fully and therefore some sensitivity can persist to remind you that there is a process at play that needs your attention. This does not mean that you do not use the tissues as in fact this is exactly what the tissues need and crave, movement.

In summary, pain is normal, it is protective and for a good reason, i.e. to motivate appropriate action. The level of pain is not related to the amount of tissue damage and the experience is produced by the brain. There are a number of responses involving body systems communicating and working together.

So why has my pain not gone away?

This section is being updated, please check back

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