How Can You Tell the Difference Between Acute & Chronic Pain?

Understanding the difference between acute and chronic pain and the type of pain you are dealing with is helpful when searching for suitable treatment. Whether it is sharp, aching, or just plain uncomfortable, getting an accurate diagnosis of your pain can be the first step to successfully managing it. Here, we'll identify what is caused by what kinds of pain, discuss common types of pain and and what actions you can take that are most helpful.

Let’s start with understanding why pain is more than what it seems.

Pain is more than our body's physical state

Wouldn’t it be great if we could tell the type of pain you have simply by looking inside your body. But pain can be caused by a variety of factors, and these are often not able to be identified from physical exams or medical scans.  

Have you been told you have disc pain, joint pain, muscular pain, nerve pain, back pain or neck pain? These terms describe where the pain is but tell us very little about the type or cause of the pain.

Pain is more than just the physical structures of our body.

Even when we see something unusual on a medical scan, this is only slightly helpful in determining the type of pain. This is because there is a lot more to the story of pain than its apparent physical structure. Nerves in the body cannot directly detect ‘physical structure’ or ‘damage’ or ‘bulges’ or ‘arthritis’, they are not designed in this way. These are still relevant but the way nerves work is more complicated than that, as we will explore later in this article.

For now, let’s recognize that pain is far less about the structures than we previously thought, and more about our body’s response to it.

To explain this further, take a look at the table below with the results of three thousand people’s medical scans (CT and MRI) taken of the spine. As you might notice, at every age bracket from 20-80 years old, there is a very large percentage of people who have degeneration, disk bulges and so on. Interestingly, all of the three-thousand people were selected for these studies because they were pain-free and the researchers wanted to know what was ‘normal’.

This shows that it can be very normal to both have these changes in your body yet have no pain.

Image of table of data showing that all types of degenerative spine imaging findings in asymptomatic patients increase with age; in particular, disk degeneration, disk signal loss, disk height loss, disk bulge and facet degeneration are extremely high in older populations.
Table showing that all degenerative spine conditions increase in prevalence with age, even in asymptomatic people.

Rather than using negative terms like ‘degeneration’ we could describe these as normal ‘age-related changes’. Having said this, we aren’t implying that changes in the body like these are irrelevant, and while they are never the only factor, they can be contributors (Brinjikji et al. 2015b). But in any case, there is always more going on that determines why some people with findings on scans have pain and some do not. Another thing that downplays the findings of medical scans, is that many people have severe pain, yet nothing on a scan helps explain it.

Pain is a complex topic, and while changes in the body can contribute to pain, they are usually a much smaller part of the picture than we previously thought (and never the whole picture). And if you have had pain for a long time, it is less useful to think about your pain only in terms of what can or can’t be diagnosed on the basis of a scan.

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What are the types of pain

There are many ways that pain experts will classify someone’s pain. Each is important because the type of pain you have will help you understand how to approach it best.

Typically, experts classify pain according to whether it started recently or more than several months ago. This classification makes a distinction between pain that is recent and more persistent pain. Pain is classified as ‘acute’  when it has been around less than three months or ‘chronic’ when it has been around longer than three months.

This time frame is related to how long it takes for body tissues to heal, and the time it takes for pain to become ingrained in a way that the ‘pain system’ itself (rather than the injury) becomes the problem.

When does acute pain become chronic

Acute pain can be easier to identify as it is often linked to injury or inflammation. Chronic or persistent pain has more complicated contributing factors.

Acute pain becomes chronic when pain continues despite the tissues healing rather than because of failed healing. This is when one type of pain stops and another starts. Below is a table of what qualifies as acute pain and what qualifies as chronic pain.

Table showing comparisons between acute and chronic pain; these differences are explained in the text below the image.

Understanding the difference between acute and chronic pain can be fundamental to getting the right treatment for your pain.

As the image above shows, both acute and chronic pain can be mild or severe, constant or varying. Acute pain has a recent onset (less than three months), and because the main cause is primarily inflammation and healing-related factors, acute pain usually has a known trigger and reduces as the tissue heals. This is in contrast to chronic pain which is pain that lasts for longer than three months, may or may not have an observable cause and continues long after any tissue damage has healed. It's important to note that whereas treatment of acute pain involves protection of the injured site, chronic pain is best treated by improving a person's overall health wellbeing, including their sleep, fitness, movement and any emotional distress.

We’re better off treating chronic pain as chronic pain, rather than protecting the painful area as though it were still injured. Protecting the area when it’s healed prevents it from becoming strong and desensitized again. Recognizing pain as chronic helps you realize that the focus of treatment needs to shift to other things.

Even so, this classification has its limits. This is because classifying pain as ‘acute’ or ‘chronic’ doesn’t tell much about your specific pain, or the contributing factors that are unique to you.

And in general, pain feels awful no matter if it’s acute or chronic. And regardless of whether pain is acute or chronic, it can still  benefit from an approach that considers: the health of bodily tissues in the local area of pain and beyond, mental health and stress-related things, sleep, and adjusting activity levels.

Pain ‘mechanisms’: going deeper into the 3 classifications of pain

We are going to go deeper into the 3 classifications of pain. And if your main takeaway from this article is understanding the differences between ‘acute vs chronic pain’ this will hold you in good stead as you take a broader and holistic approach to your pain and well-being.

Beyond the acute and chronic distinction, pain can be classified by what is happening in, around, and between nerves. This means nerves extending into the tissues of the body, as well as how signals are being transmitted, processed, and amplified within the central nervous system. This way of thinking has led to the classification of pain as nociceptive, neuropathic, and nociplastic pain.

Nociceptive pain

Nociceptive pain relates most strongly to signals coming from the body. This can be due to nerves detecting high or low temperatures, certain chemicals like those that make up inflammation, and mechanical pressure such as stretching or compression.

Nociceptive pain is the main type of acute pain, but can still have a limited role in some types of chronic pain. As previously noted, there are no nerves that detect ‘damage’ or ‘bulges’. This means that if a problem in the body contributes to nociceptive pain, it must be because it causes inflammation, which are the chemicals that sensitize nerves. And/or because the physical changes cause physical pressure on other tissues.

These are things we can change or adapt to.

Firstly, the body adjusts to changes in physical pressure. This means that as long as we keep moving, our body will adapt to changes in physical structure such as a disc bulge. Secondly, the influence of inflammation will be strongest at the beginning of an injury, and will diminish rapidly over time.

Notably, ongoing pain states can be influenced by low levels of ongoing background inflammation. And background inflammation can be influenced by things that we can address, like stress. But the important message here, is that if pain has been around longer than 3-months (i.e. is in a chronic phase) nociceptive pain will rarely be the main, and certainly not the only, cause of pain. So when pain persists, we always have to think about addressing ‘other’ types of pain.

Nociplastic pain

Nociplastic pain is pain that relates strongly to changes in the nervous system that then amplify signals from the body. Just as you learn a new skill with repetition, the nervous system is designed to get better with practice. The nervous system can also become effective at producing pain. And as the nervous system is also keen on protecting us, it can be reluctant to reset it’s sensitivity level back to normal even when the need to protect our body has passed.

One helpful way to define nociplastic pain is that it is pain that has outstayed its protective usefulness and is due to sensitizing processes in the nervous system that amplify information from the body. These sensitizing processes in the nervous system are the main cause of chronic pain. While amplification of signals from the body is also a part of acute pain, the problem in chronic pain is that these sensitizing processes that developed during acute pain fail to go back to normal.

Neuropathic pain

Neuropathic pain only occurs where there is specific damage or disease of the nervous system itself. You’ll know that this is a part of your pain if you have had a specific nerve injury or neurological condition and have a loss of sensory function. For example, numbness of the skin and or a loss of muscle control.

What are the signs & symptoms of different pain types?

Take a look at the checklist below. Seeing how many things you tick/don’t tick in each will give you some idea of how much of these three ‘pain types’ are a part of your particular problem.

Table showing comparisons between nociceptive, nociplastic and neuropathic pain; these differences are explained in the text below the image.

Nociceptive pain has a recent onset and is localized to the injured site. The pain intensity diminishes over time and the pain response is predicable and proportionate to the triggers. On the other hand, nociplastic pain is prolonged, may be hard to localize and is often unpredictable and out of proportion (for example, it may be easily triggered by gentle touch or movement). Finally, neuropathic pain comes with a history of nerve damage and a loss of sensory and motor function. It often presents as pins and needles and the pain or sensory changes will follow the path of the damaged nerve, such as with a shooting or burning pain down a limb.

These different pain mechanisms can overlap.

For example, someone might have chronic low back pain that is mainly ‘nociplastic’. This is related to the nervous system amplifying its signals from the back. But, the local tissues in the back might also be sensitive due to some local tissue irritation causing inflammation.

This inflammation would lead to some nociceptive contribution, since inflammation sensitizes nerves that are then easily triggered by physical pressure during movement.

This same person could also have some nerve injury or irritation causing some neuropathic contribution.

This is helpful to know because a clinician like a physiotherapist might be able to help determine if there is a way to reduce irritation in the lower back. They can also improve tissue health and tolerance in that area so that it doesn’t get so easily irritated.

It is great to think about this as one part of your treatment that can be added to other important treatments aiming to improve your mental and physical health. Combining these approaches is the best way to address both nociceptive (issues in the tissues) and nociplastic (amplification in the nervous system) components.

Classifying based on ‘pain mechanism’ when considering your ‘pain type’ is helpful because it stimulates you to think about a wider range of contributors to care and recovery. Moreover, it can help you understand whether your main focus should be on facilitating healing from an injury, or on calming your nervous system and re-conditioning your body.

Regardless of pain type, the important thing is to look at a range of contributing factors such as the health of bodily tissues in the local area of pain and beyond, and to identify where you can optimize things like mental health and stress, sleep, and activity levels.