Pain is actually a topic we haven’t touched on much in any of our posts. Not because it is unimportant, but because it is and there is already an abundance of pain-related articles and discussions on the internet that are mostly recent and accurate. We’d like to discuss common pain issues that we see in an easy to understand short format.
We will not touch on the subject of chronic or persistent pain in this post, as there are other resources available that have more detailed information with regards to persistent and chronic pain. However, in short, persistent pain is pain that is lasting longer than the expected recovery time and chronic pain is pain that is lasting over a long period of time (duration & definition varies).
What is pain in the first place? The International Association for the Study of Pain (IASP) defined pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage”. Simply put, pain is a signal that you receive when the body thinks it is being damaged or in danger of being damaged. This is inherently different from actual damage. The damage itself sends signals to the brain, and the brain interprets it as pain if it deems appropriate, the signal itself is not pain. When we stand on a thorn, we feel pain in the foot. There are sensors (nociceptors) in our foot that detect a harmful stimuli (e.g. the thorn), producing a signal called nociception. The signal travels to your brain and the brain translates the nociception as pain. This serves as an alert to the organism (you) to protect it. Alternatively, if you stand on a less sharp but thorn-looking object the brain may perceive it as a danger and create pain to warn you despite no nociception signal being received.
The example above shows that the intensity of pain experienced does not directly correlate with the extent of damage. The danger of the thorn-like object can cause pain without damage, and nociception has to be interpreted by our brain as pain, which is not always proportional to the damage. Psychological factors such as existing beliefs, stresses, and previous experiences changes how the brain may interpret that stimuli (e.g. nociception); for example if you have had a previous injury from a thorn and needed to go to hospital and had a very hard time with recovery, it is likely that the brain will increase how painful it is because it recognises based on previous experience that thorns are dangerous and increase the pain output.
This is not the only case why damage may not be proportional to the pain perceived. Another example is less to do with the brain but more to do with the structure. If we take a ligament in the ankle as an example, when you sprain an ankle, that ligament becomes damaged by it being overstretched. With a micro to partial tear, it is often painful because in certain positions that ligament gets stretched, there are sensors that detect that stretch. The brain then interprets that stretch as harmful or dangerous for a ligament that is already overstretched. However, if the ligament is completely ruptured/torn during the injury, it is usually less painful. This is because the ligament is, well, completely ruptured, there is nothing to be stretched, so the sensors do not detect that “harmful” stretch. Obviously, the completely ruptured ligament has a worse damage compared to the partial tear, but the body is unable to detect it, hence less pain. Damage is not always proportional to the pain - sometimes the pain is worse than the damage, sometimes the damage is worse than the pain. Diagnosis must be performed to determine what is damaged and to what extent.
Nociception is the signal that is transmitted by nerves when a harmful stimuli is detected (thorn), which often results in what we call “nociceptive pain”. Neuropathic pain is different as neuropathic pain occurs when the nerves themselves are damaged/irritated, rather than the nerves/sensors detecting damage. As a simplification, (peripheral) nerves carry signals to (afferent)and from (efferent) the brain and spinal cord to the rest of the body, affecting the function of one or more nerves sending pain messages to the brain. Damage to nerves can cause: pain (damage is present) or disruption of signal transmission. When an afferent signal such as sensation from the skin going to the brain is disrupted, the sensation you feel on the skin may be altered, some people would describe it as numb, dull, tingling. When an efferent signal such as a command from the brain to a muscle is disrupted, the muscle will not be able to work normally, this can be felt as weakness or tremors/shaking. Neuropathic pain itself is generally described as burning, shooting, or electric-shock like sensation.
Neuropathic pain or damage can happen in various ways. It could be a medical issue, such as diabetic neuropathy and multiple sclerosis, or aside-effect of treatments like chemotherapy. Nerves can also be damaged mechanically, usually a high-impact injury onto a nerve that is closer to the surface, or a compression-type mechanism such as a bulging disc pushing onto a nerve. However, some of these may behave mechanically or non-mechanically. Most medical issues will cause neuropathic pain that is non-mechanical, meaning movement does not change the pain. Most physical injuries will result in mechanical neuropathic pain (e.g. pulling on the nerve makes it sore). Similar to nociceptive pain, the intensity of pain is not always proportional to the damage, it indicates diagnostic testing needs to be performed to determine what is damaged and the extent of the damage.
While there isa third descriptor of pain: nociplastic pain, it is a new mechanistic descriptor of pain and we will not touch upon this third mechanism at this stage. However, hopefully, this gives some insight to your injury or pain. Regardless of the pain type, the intensity of the pain does not describe the extent of damage and would require a clinician to reach a diagnosis to be certain. This does not replace a medical advice, if you have pain and you are unsure, please approach your local clinician for assessment and treatment.