Pain Without An Injury? And How To Calm An Overactive Pain System

When we think of pain, we usually think of injury or illness, but it's actually common to experience real physical pain without an injury being present!

It’s natural when we think about pain to associate it with hurting yourself, typically we think of an injury which causes pain. However, pain can occur without any injury, or even after an injury has healed. Essentially this is what chronic pain is: pain that is ongoing for a long period of time, typically thought to be three months or more, having passed the usual healing time. 

This can either occur without an injury at all through chemical imbalance, or a healed injury can leave behind neural pathways which continue to create the pain experience. In this situation, the pain response becomes wired in the brain and nervous system. Although it’s not all doom-and gloom. For many people, it is possible to train the brain and body away from pain.

What is central sensitization?

Your pain system being overactive or too sensitive, means that the parts of the brain and nervous system that are supposed to be controlling how your body feels pain, are not acting appropriately. Your autonomic nervous system, which is what gives out these signals, is divided into two parts: the sympathetic nervous system and the parasympathetic nervous system. While the sympathetic nervous system is designed to send out pain signals at appropriate times to get the body ready for action, the parasympathetic nervous system is designed to calm these pain signals, to relax the body when pain doesn’t need to be felt, so that the body is experiencing pain in an effective and normal way. 

When chronic pain comes into play, the nervous system is stuck in a ‘fight or flight’ response, meaning that these two systems are functioning on overdrive and are not giving out the pain signals in the way that they should. This is also known as central sensitization, or central amplification, because the central nervous system is too sensitive and the signals are amplified. This study explains that,

Central sensitization is known as an increased central neuronal responsiveness and causes hyperalgesia, allodynia, and referred pain and hyperalgesia across multiple spinal segments, leading to chronic widespread pain.

Chronic pain changes how your nervous system works

Chronic pain is essentially changing how your brain and nervous system work, becoming a disease in and of itself. Our brains and nervous systems are neuroplastic, which means that they adapt as we grow and learn about the environment around us, to help us to function optimally and keep us safe. Chronic pain is continually stimulating the nervous system which detects, sends and receives pain signals, and by constantly stimulating these pathways, is literally changing the structure of the nervous system, in turn making it more active and over sensitive.

Pain is designed to protect your body, to keep you alive: it tells you when you need to rest; when there’s danger and you need to stop that action, for example if you touch something too hot and you need to move your hand away to avoid a burn; or when there is something wrong with your body that you need to pay attention to and seek medical help for. 

The nerve endings all over your body called nociceptors, when faced with any situation, communicate with your brain and make an assessment based on the information that they have, about what is best for the body; they decide whether there is a dangerous situation and you need to feel pain in order to protect your body from it, but this may not be the right assessment. If there is a chemical imbalance or the brain has had a previous significant experience that caused pain, the wrong signals may be sent out and you may feel pain when you do not need to.

Chemical imbalance can cause pain

Chemical imbalance can be caused by stress and becomes an ongoing cycle wherein stress causes pain and pain causes stress. The science of this cause of pain is less understood than that caused by a previous injury, but is being researched more all the time. It’s thought that ongoing stress and other emotional and environmental factors cause the body to ‘think’ that it needs to send pain signals as a defensive mechanism, therefore sending out the wrong chemicals around the body.

Let’s look in more detail about how stress can cause pain. Stress is normal in everyday life but when a person is going through constant and ongoing stress for a long period of time, this becomes a problem. Stress causes the brain to put your body on high alert, because something is wrong and there could be danger, meaning you are in the ‘fight or flight’ state of mind: your sympathetic nervous system is ready for action, prepared for danger, meaning your heart rate and blood pressure are increased while your blood flow is redirected, focused more on your vital organs, ready to tackle whatever danger could be ahead.

If your body is stuck in this situation for an extended period of time, it can result in you feeling worn out and exhausted, as the body is not designed to cope with this sort of prolonged emotional intensity. This can in turn result in your muscles feelings tight, you feeling achy and sore, your blood pressure being high and headaches occurring among other symptoms: the pain response has begun. From there you are stuck in the stress and pain cycle: being in pain causes stress because it is hard to deal with and has a big effect on your life, this stress then perpetuates the pain you are in and so on.

A healed injury still causing pain?

In regard to a previous injury that has healed but left pain behind, the nervous system may think that it is protecting you from a dangerous situation. Just like your mind and body learn things as you grow as a person and adapt to life, so do nerve pathways change as they learn how to react to certain situations. These lessons, however, may not always be the right ones.

An injury can act as a catalyst for ongoing pain, initially causing your nervous system to send signals back and forth to your brain in an appropriate way to tell you the injured part of your body is hurt, but once the injury is healed the nerves are accustomed to sending those pain signals, and persist in doing so, even though there is no longer any need. 

For example, if you were typing a great deal over a long period of time and this caused RSI (Repetitive Strain Injury), then after this instance, when you go to type your mind now perceives typing as a dangerous situation that you need to be protected from, and so sends pain signals out; as a result, typing becomes painful. Your brain thinks it’s doing what is best for you, protecting you from something that has hurt you in the past and therefore is a threat. This study states that,

injury, even mild injury, may lead to long-lasting changes (sensitization) in the nervous system—from peripheral receptors to the cerebral cortex—that may produce persistent pain in the absence of ongoing nociceptive stimuli.

Pain creating behaviours

Behaviours, thoughts and environmental factors can alter your perception of pain and perpetuate the pain cycle, fueling the chronic pain and keeping it going. Let’s take a look at some of the factors that can perpetuate that pain cycle:

  • Pain catastrophizing: this essentially means worrying about your pain, whether the pain in the present or anticipated pain in future. It’s natural when you are in a lot of pain to be worried about it; to overthink, to worry about what is causing this pain, worrying about how your actions may affect your pain, thinking the pain may last forever, and so on.. However this catastrophizing about your pain is actually making it worse. Learning to change these thoughts and empower yourself, can aid in breaking this cycle.


  • Avoidance: if a certain situation has worsened your chronic pain in the past or caused your initial injury, or if there’s an action you perceive as something that may increase your pain, then it’s natural that you would want to avoid those situations, but by avoiding them, you are contributing to compounding this pain cycle. By facing situations head on and changing your mindset, you can be proactive in breaking this cycle. 


  • Limiting movement: if you’re in pain a natural reaction is to feel that you should not be exercising or ‘overdoing’ things, but by limiting movement and restricting your functioning, the pain cycle continues and even worsens because your muscles aren’t being used as they should be and can weaken. Learning to exercise and move your body in a way that suits you and at a pace that will work for you, can be highly beneficial in managing your chronic pain and working towards recovery.
  • Social isolation: as with limiting movement, if you have a perception that your functioning is lower because of your pain, then it can be common to not engage socially because you don’t feel able. This can cause depression and anxiety, which again compounds the stress and negative emotions causing pain. Ensuring that you are maintaining connections and being actively social is very beneficial.
  • Poor diet: while a nutritious diet isn’t going to cure your chronic pain, having the nutrients that your body needs to function is vital and is how we keep our bodies functioning in a healthy way; this becomes even more important when you have extra health concerns like chronic pain. Having a poor diet that doesn’t give your body all it needs to function, only adds to problems like inflammation, a lower immune system and a lack of energy among others. Maintaining a healthy diet can help to manage symptoms and set your body up for success. This study showed that,

When diet is combined with exercise, there is a consistent reduction in pain.

  • Lack of sleep: sleep gives us the energy that we need to function, when it’s disturbed as is so common with chronic pain, it can add to the fatigue and other symptoms that a patient is feeling and perpetuate that cycle. As you work on reducing pain and getting a more effective sleep cycle, the two tie in together to help you to feel more energized and able to function.

Calming your overactive pain system

Treatment of chronic pain needs to focus around breaking this pain cycle, reducing these pain creating behaviours and thoughts, and helping patients not only to understand their pain and how it works, but how to overcome it and live a healthier life. It isn’t an easy road and there isn’t a quick fix; thinking more positively isn’t just going to cure your pain straight away, but by learning how to manage your pain and how to break this cycle over time, you can regain that quality of life that you may have lost and not feel limited by your condition.

CBT (Cognitive Behavioural Therapy) among other therapies, are a great way to get that help you may need to understand your pain and change those behaviours, replacing pain creating behaviours with positive behaviours that help you to reduce your pain and live the life that you deserve.

Chronic pain and chronic conditions must be treated as their own individual problems in their own right by medical professionals, and be researched more as such, rather than pain being thought of only as a result of an injury. This is how chronic pain patients can get effective diagnosis and treatment, how they can get help to break the pain cycle and not just survive but thrive.

Please note: This article is made available for educational purposes only, not to provide personal medical advice.


  • Practical Pain Management, Volume 15 Issue 4, Beth Darnell, PHD., (2015),  “Targeting a Saboteur of Surgical Outcomes: Pain Catastrophizing”.
  • Clinical Rheumatology, Volume 26, Issue 4, pp 465–473, Mira Meeus, Jo Nijs, April (2007) “Central sensitization: a biopsychosocial explanation for chronic widespread pain in patients with fibromyalgia and chronic fatigue syndrome”
  • Pain, Paul Ingraham, (2019), “Sensitization in Chronic Pain”
  • Pain, Paul Ingraham, (2019), “The 3 Basic Types of Pain
  • MSD Manual Professional Version, Mayo Clinic, James C. Watson , MD., (2018), “Chronic Pain” Institute For Chronic Pain, Murray J. McAllister, PsyD, (2013), “What is Central Sensitization?
  • J. Chua, S. Ishihara, M. Riad, I. Castrejon, R. Miller, A.-M. Malfait, J. Block, N. Shakoor, (2019), Peripheral and central sensitization and neuropathic pain are present in both osteoarthritis and rheumatoid arthritis”

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