We often ask ourselves “Why does it hurt so much? I haven’t done anything! What is pain?” In this article, we have put together a few facts that may help you understand what pain is and how it is generated. We also investigate what it means in terms of treatment and self-help.
What is pain?
According to the International Association for the Study of Pain, pain is
an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage
Two things are of note in this definition:
- Pain is an experience, it is subjective and always real for the person who experiences it.
- We experience pain in a manner that suggests tissue damage, that is we hurt in certain places of our body.
The nervous system
In order to understand how pain works, we need to have a look at a few aspects of our nervous system.
There are several parts that are relevant to pain:
- The nerve endings (receptors) that generate signals
- The nerves that collect signals from the nerve endings and transfer the signals to the spine
- The nerves that transport signals up and down the spine
- The nerves that transport signals around the brain
- The nerves that transfer signals from the spine to organs, muscles and other tissues throughout the body.
The various neural receptors, which can be found all around the body, register different events in the body, such as touch, temperature, movement and spatial orientation, and pain (damage to tissue).
The signals from receptors called nociceptors are the ones relevant to pain. Nociceptors are located in the skin, viscera, muscle, fascia, blood vessels, and joint capsules and they register if there is damage to tissue.
Let us look what, for example, happens when you stub your toe:
- Nociceptors register tissue injury and send signals through long nerve cells up to the level of your spine. The signals are transferred into the spinal cord and from there up the spinal cord to the brain.
- The brain processes the signals and generates the appropriate output
- You pull back and lift the foot
- Ouch! It hurts
- Inflammation sets in in the toe (this is the natural healing process). As a result, nociceptors generate signals that result in increased pain sensitivity around the toe. It may now hurt if you just touch it.
- You adapt your gait and don’t stand on the injured toe.
How much it hurts and whether the pain is sharp, constant or throbbing depends on various factors that can modulate pain.
Whether and how we perceive pain depends on a number of factors. The processes involved are often referred to as pain modulation.
One way in which signal strength (how much it hurts) can be influenced is how frequent a nociceptive signal is generated and/or on how many there are of them. Inflammation, for example, can influence these factors.
Another pain modulation process takes place at the neural junctions, that is at the locations where signals are transferred from one nerve cell to another. There are many factors that can influence the signal transfer.
To understand this, we need to look how such junctions work.
When a nerve signal reaches the end of a nerve cell, chemicals are released into that watery soup that makes up our body. The beginning of the next nerve cell is placed very near to the end of the previous cell and the released chemicals float across to this cell, bind to it and effect a new neural signal that then moves along this nerve cell.
These special chemicals that are released at a neural junction are called neurotransmitters, and how effective this signal transfer works relates to how you perceive pain. Reducing this effectiveness reduces your perception of pain, and this is how, for example, an opioid pain killer works. It reduces the number of nociceptive signals that are transferred.
There are several areas in our body where neural junctions are concentrated.
These are a kind of collection points of the peripheral nerves, i.e. the nerves that supply all our body.
The different kinds of neural signals are transported in various dedicated pathways up and down the cord. The signals are transferred to and from the root ganglia to these pathways.
The brain is mainly a collection of interconnected nerve cells.
Ways of influencing pain signals
Experts often talk of sensitisation in this context. That is, you become more or less sensitive to neural pain input.
A central mechanism is the feedback loop. Signals move up the spine into the brain, are processed and as a result signals are sent down into the spine that influence the effectiveness of signal transmission in the spine. Signals that subsequently come into the spine may be generally enhanced or weakened.
Some conditions in the body may have a similar effect, e.g. inflammatory conditions or nerve damage can increase sensitivity in the spinal cord.
But the key lies in the activities of the brain. What then actually influences these brain functions? What makes us more or less sensitive to pain?
One well-known influencer are opioid pain killers.
Another “natural” influencer is apparently our mental state. Here are a few conditions and sensations that are known to influence pain sensitivity:
- Our current mood
- Chronic pain (this is a kind of a vicious circle.The more pain we experience and the longer we experience it, the more sensitive we seem to become to pain.)
- Expecting pain
- Fear of pain.
Dealing with pain
The following applies to musculoskeletal conditions.
The first priority is to try to eliminate the cause of the pain. But establishing the cause is often not that easy.
If you just stubbed your toe, the case is clear (but even in this case, the intensity of the pain may be influenced by various other factors). But what if you have some indiscriminate back ache that seems to come on for no apparent reason? And what about those headaches or migraines? It is important to keep an open mind and, reminding ourselves of how pain sensation works, we have to consider all factors that can contribute to pain.
From a therapists point of view, the first priority is to establish possible contributing factors. Are there any known conditions or functional restrictions that cause the pain, such as muscle or tissue pain, joint pain, pain with certain movements? What about the patient’s environment? Are there activities that may cause the problems? Are there events or situations that negatively influence the patient’s mental state?
The second priority is to establish the factors that we can influence. “We” meaning the therapist (or any other medical person) and/or the patient.
Once we have established this, we can devise a way forward: What can the therapist do? How can the patient contribute? What can be done short-term, what in the long run?
Having said all this, we often do not know exactly what causes the pain and we just have to work on the factors we know.
Prevention usually has two components:
Periodic treatment to
- Identify and remove tensions and restrictions in the musculoskeletal system
- Reiterate patient activities
- Monitor progress in tackling other factors that contribute to pain situations.
- Becoming aware of activities that may cause the problem (posture, remaining in the same position for long periods etc.)
- Adapting elements of one’s environment (adjusting car seat, office chair, changing your sleeping position etc.)
- Exercising (specific exercises that address known causes of the condition)
- Adapting specific aspects of one’s lifestyle (tai chi, yoga, regular exercise etc.).