Chronic pain is very different from acute pain. With acute pain, you injure an area, it swells, it hurts, movement makes it worse, rest and nsaids make it better, the tissue heals and the pain goes away. Simple.
With chronic pain the pain doesn’t go away; at least not permanently. It goes away, it comes back, it gets worse, it stops making sense, nothing seems to make it better, everything makes it worse, you may lose your sense of control and the process continues.
But first lets start with a couple definitions.
Nociceptor: A sensory receptor that detects actual or potential tissue damage.
Pain: Suffering or discomfort caused by illness or injury.
Pain also has two components two it. The objective component (this is where it hurts and this is how much it hurts) and the subjective, or emotional, component; the person’s suffering; how much the pain bothers you. It is this component that makes chronic pain especially unique and, very often, devastating.
When you overstretch tissue or bend a joint in a direction it shouldn’t go you will activate nociceptors that will send signals to your brain letting you know that there’s some potential for tissue damage about to occur. The more you bend or stretch the stronger the signal and the increased likelihood that your brain will interpret those signals as pain.
Depending on the context, your given situation may affect how strongly, or how quickly, your brain interprets those signals as pain. A soldier at war, who loses an arm is very unlikely to experience any actual pain because he has more important things to deal with (like getting out of gun fire). Once he’s relatively safe, now his missing arm is the most important thing for him to pay attention to and it will start to hurt like hell… but only now that the context of his injury changed. Your brain will prioritize pain, and other perceptions, based on their importance.
In another scenario, if you expect something to hurt like crazy, even if it’s completely innocuous (an acupuncture needle is a common example), then you are very likely going to perceive pain even though very little nociception was actually sent from that body part. The pain is still real, because all pain is created within the brain based on all the available information, but this person’s pain experience could be radically changed just by having a different understanding of what an acupuncture needle is and does. Fear can very powerfully manipulate pain.
Consider two patients who have an identical low back injury and have identical health overall. If one of them is terrified of being disabled later in life and the other isn’t worried one bit the first person is going to be in significantly more pain due solely to his or her fear of being disabled. It increases the prioritization process in your brain so that you experience more pain so that you spend more time and effort to deal with this situation.
In parts two and three we’ll continue discussing the biology pain, why it becomes chronic and what can be done to eliminate it.