For a long time, we have viewed pain as a sign of injury or damaged tissue and have relied on models that are largely based on basic anatomy and physiology. These have been at best, simplistic cause and effect mechanisms where an injury to a particular body part, such as a tendon or muscle tear, disc bulge or joint sprain will result in pain. This of course is true to some extent, but it only explains one piece of the puzzle. It doesn’t account for other pain phenomena such as chronic pain – pain that persists for longer than the time it takes the injury to heal, or why two people with the same injury, may have a completely different pain experience.
When we think of pain, we think of nociception. These are receptors found throughout our body that detect “potential damage” or what is referred to as a noxious stimulus. We send signals to the brain and central nervous system (CNS) via nociception to alert us of the potential harm to our body tissues and intern we feel pain – something hard to ignore, so we will do something about it. But what is pain? If it were simply a sensation, similar to touch or vibration, then the more tissue damage, the more nociception activation, the more pain we feel.
But it's not that simple. We now know that pain is not a sliding scale of detection leading to pain. There is no clear relationship between the amount of tissue damage and the level of pain that we feel. Sometimes it works in reverse and to our advantage. Think for a moment about reports catastrophic trauma, where a person reports feeling no pain at all, despite having suffered the most horrific injury that you would expect to cause an unbearable level of pain.
So, when it comes to our pain experience, something isn’t adding up, and the answer lies quite literally in our heads.
Pain is now being viewed as an output behaviour in response to the need for protection. In fact, it is more similar to an emotion, rather than a sensation. It (pain) is something that is 100% of the time produced by the brain. The missing link between the detection of a noxious stimuli (something capable of causing tissue damage) and the unpleasant painful experience of what we feel lies in a number of different areas of the CNS collectively called the Central Pain Neuromatrix. Parts of the Neuromatrix include the spinal cord – centres for reflex-analgesia, the brainstem for autonomic reflex control and descending pain inhibition, limbic areas for fear and memory, conscious cortical areas for perception, and motor cortex areas for taking action. All these areas receive nociceptive information coming in from our parts and scrutinize their significance based on past experiences, beliefs and understanding around their own condition, fear and anxiety levels which may be heightened due to the significance of the injury to career or context. The output from the Central Pain Neuromatrix can then go on to alter function of the sensory, motor and autonomic systems which means the end result, an and extremely unpleasant and memorable experience produced with the aim to modify our behavior and protect us from harm can be up- or down-regulated...Can you see how this is becoming more personal now?
What this means is that everyone’s pain experience is different, because everyone is different. Past injuries and experiences, our belief systems and our understanding of the injury at hand will all effect the pain output we feel. On top of that, our daily stress, fear and attitudes we have will all effect pain levels and ultimately their progression. It is a very sophisticated and specialised system that we should be thankful for. After all it is designed to protect us and responsible for our survival. However, sometimes the system gets it wrong and we end up experiencing more pain that we should, or for longer and that of course is a situation most of us don't want to find ourselves in. This is why it is important to get to know your body and what is happening when you are in pain - get to know your pain neuromatrix. Education and understanding will help to reduce fear and that will go a long way in the journey to recovery.