What is pain? It might not be something you’ve really thought about but it seems like a pretty easy answer – you stub your toe, it hurts. You touch a hot burner, or you roll your ankle and they hurt immediately. Pretty straight forward right? Pain is your body’s response to physical danger. Your brain receives a signal, whether it’s the crushing impact on your toe, or the heat from the burner on your skin and interprets those stimuli as a danger and creates a pain experience to alert you that something is wrong. In this way, pain is crucially important to our survival. People with decreased sensation can suffer serious consequences due to their inability to feel pain. Makes sense right, trauma = pain. Thank you Captain Obvious!
Not so fast….
Pain is easily explained in acute situations like the ones above, but how do we explain pain that lasts for weeks, months or even years? Low back pain is a common example. Maybe you hurt your back picking something up, or you sleep in a weird position and wake up hardly able to move. For some lucky people this pain will last a matter of weeks and disappear, but unfortunately they’re the minority. For many others, the pain will continue to persist. We know how long various tissues take to heal, so how can this pain still remain long after those expected healing times have past? (Note: this cycle is often incorrectly attributed to continuously re-injuring the affected area but this isn’t always the case).
The answer lies in our brain, or more precisely, our entire central nervous system. We once believed that we had specific pain receptors all over our bodies but this isn’t entirely correct. What we actually have are called nocioceptors and can be thought of as your “danger sensors”. These receptors are simply sensors that monitor for a variety of potentially harmful stimuli and are responsible for alerting the brain. When we touch a hot stove our nocioceptors sense the increase in temperature but that’s all the information they know. They can send a “we’re touching something warm” signal to the brain but it becomes the brain’s job to interpret this signal. If your brain decides that it’s just warm, but not hot enough to damage your skin, it responds by inhibiting the original signal and you don’t feel any pain. However, if the brain decides that the temperature is enough to cause damage, your brain creates a pain signal and you will instinctively pull your hand away to protect the area.
So, if it’s the brain’s interpretation of these constant danger signals that can result in an experience of pain, why does your back still hurt 6 or 12 months after the initial injury? Longstanding pain is due to a process known as “sensitization”. This can happen in two places: First, at the original site of injury, the sensors around the injured area become more sensitive as they become accustomed to sending increased signals. Their increased input continues after the physical damage has resolved but the brain isn’t aware that the healing process is complete and continues to produce a protective pain response. This can occur to a stimulus as simple and harmless as light touch or movement. Secondly, changes can occur within the brain itself. The brain has designated areas for each and every body part and these areas are able to adapt and change over time. If the area for the low back is being constantly stimulated by danger messages, this area can grow and even start to overlap with surrounding areas. This can cause movement in other areas of your body to trigger danger messages that the brain interprets as originating from the back, and again you feel pain. This feeling of very real pain in the absence of true physical damage is what we know as chronic pain.
The good news….Both of these processes are completely reversible! The first step is understanding the complexity of the pain process are realizing that there may no longer be a physical injury. Then you can begin the process of re-training the brain and desensitizing the nervous system to restore a pain-free state!
It’s important to understand that this article only covers the physical mechanism behind pain. Pain can also be affected by non-physical elements such as emotional and social factors but that’s a subject for another blog! If you have longstanding aches and pains you may be suffering from chronic pain. Drop by and have a chat with your local physio to determine the appropriate treatment method to get you back on your feet!
This article originally appeared on Stoke Physio.