There continues to be mis-conceptions about pain and whether or not the body has pain receptors and nerves so I wanted to go back and describe a bit of history and what we currently know and understand about pain.
There were 2 dominant biomedical perspectives on pain. The first perspective was called the “specificity theory” where in order to experience pain, a specific pain receptor had to be activated before it sent the signal up the nerve to the spinal cord and finally ended at the brain. Only pain receptors and pain nerves could send signals informing the person of pain.
The second theory was called the “pattern response” whereby the pain signal did not come from a specific receptor but rather from general receptors in the body. Meaning the same receptor could send signals not related to pain or could send signals related to pain depending on the pattern of activation. This means a gentle touch of the skin is a different pattern than pressing a hot spoon on the skin. Either signal experienced in the body came from the same receptor.
Both of these theories had problems explaining the pain experience and were quite simplistic in their explanation.
What we know now is that there are no specific pain nerves or receptors in the body. Pain is a more complex experience that takes into account all the information from our body, our past experiences and attitudes towards pain and the brain must make sense of all this in order to determine if the experience in the body is…or is not painful.
Going back to receptors there are actually 3 kinds of receptors: temperature, chemical and mechanical (vibration, compressions, stretch). Within these receptors we have built in nociception. Fancy word. Nocicpetion is the signal that something is happening to the body that may be potentially dangerous to the tissues or that actual tissue damage has occurred. For example when you place your hands under running water, as the water warms up you detect change in temperature, as it gets hotter it starts to feel uncomfortable and even painful way before you burn yourself. If you continue to keep your hand under the hotter water then, yes you may actually cause tissue damage by burning yourself. So what the brain receives is information of hot, hotter, really hot, etc. But who determines that the information is ouch?
So pain is better understood as a subjective response to sensory information, meaning what we are feeling in our body, will be understood and experienced differently by different people. Some people love hot tubs, while others find it too hot and uncomfortable, the “ouch” is subjective.
The current theory of pain is called the neuromatrix theory. In this theory, pain is a multi-faceted experience that is an output from the brain. We experience pain, once the brain has decided that something threatening has happened or is about to happen. Pain is an alarm system to warn us and gain our attention.
Pain comes from the brain, but this does NOT mean it’s in your head, as in “not real.” The brain is getting information in the form of sensations, those sensations are real! At the end of the day, the brain decides what these sensations mean. Without a brain, without consciousness you cannot experience pain. Pain is complex and treating it requires the healthcare provider to undercover the layers of the onion so to speak and in some cases treat multiple things simultaneously. Science doesn’t know everything about pain but this new theory gives us greater insights to look at pain more holistically.
With these new insights from the neuromatrix theory, a new approach has emerged in physiotherapy for treatment, which is called the biopsychosocial approach. This approach takes into consideration both disease and illness, whereby illness is a complex interplay between biology, psychology and social factors. Let’s break these down.
Pain is influenced by biology, which includes our genetics, tissue damage, presence of inflammation and other healing properties. As physiotherapists we need to assess and treat any issues around the joints, muscles, nerves or fascia, taking into consideration the injury and genetic factors.
Pain is influenced by psychological factors such as, anxiety, depression, anger, negative affect (negative moods/perspectives/glass half empty thinking), our beliefs and perceptions of what pain is, fear beliefs, avoidance beliefs, perceptions of control and level of self-efficacy, which means your belief in yourself to complete a task or produce a desired outcome. All of these impact how we can make sense of the sensations in our body.
As physiotherapist we need to educate patients about pain, what’s happening in their body and teach them ways to move and resume normal day to day activities without fear of injury or re-injury. We have to identify the patient’s beliefs, perceptions and understand what they think is happening, educate and when appropriate seek collaboration with other healthcare providers. As physiotherapists, we are here to guide you, teach you how to move your body safely and build confidence and trust in your body.
Pain is lastly influenced by social factors such as, cultural beliefs and norms, the types and number of positive versus negative relationships, economic status, educational status, level of support, stress and more. So here, the way you respond or react to pain will be influenced by how your parents, friends, relatives respond to pain. We are social beings that learn from others. We also need support and acknowledgement. It’s hard to heal and recovery when people don’t believe in your pain and this includes healthcare providers. It is also difficult to recover when you are isolated and lonely. These are important factors to consider.
As physiotherapist, we need to identify what other factors may be causing the body to tense or move inappropriately, although we are not actively treating social factors, knowing what they are helps us make appropriate referrals to other healthcare providers and provides opportunity to educate patients about the impacts of social factors, hopefully motivating them to take a look at their environment and make appropriate changes.
References:
Gatchel, R.J et al. 2007. The Biopyschosocial Approach to Chronic Pain: Scientific Advances and Future Directions. Psychological Bulletin 133(4): 581-624.
Pearson, Neil. 2007. Understand Pain, Live Well Again: Pain Education for Busy Clinicians & People with Persistent Pain. Life Is Now: Penticton, BC, Canada.