Understanding Chronic Pain

Understanding Chronic Pain

If you’re reading this, my guess is that you have some experience with chronic pain. Perhaps you experience chronic pain yourself, or maybe you know someone that does. Regardless, I think that it is so important to truly understand chronic pain and what contributes to it, so that it can be better managed.

As a physical therapist, I see a lot of chronic pain. And let me tell you, it’s pretty darn complex. Management of chronic pain is multifaceted. Sure, it requires “traditional” PT modalities (manual therapy and corrective exercise), but it goes beyond that. I coach my clients in lifestyle changes that help to reduce their pain (e.g. nutrition, sleep, stress management). In fact, the complexity of chronic pain is what inspired me to go to nutrition therapy school. There is also a huge psychosocial component to everyone’s pain experience, which must be addressed for effective pain management.

It’s important to note that pain is actually a good thing. Let me explain: Pain draws our attention to areas that need healing and it motivates us to do what it takes to let them heal. If you sprain your ankle, those pain signals keep you off of your foot and motivate you to rest or seek treatment, thereby allowing the ankle to heal.

In order to really understand chronic pain, it’s necessary to first define pain. Traditionally, we think of pain being a sensation that is caused when we have tissue damage that stimulates nerves, which travel to our brain.  But, I prefer to explain that pain is not an input to the brain, but rather an output from the brain. In other words, pain is a perception, and in order for something to be perceived, it must be brought to our conscious attention. Our brain is constantly being bombarded with information (e.g. temperature, chemical and mechanical information) from our nerves, but we don’t attune to all of this information.  For example, were you aware of the sensation of your shirt on your back? Maybe you are now that I’ve brought your attention to it, but most likely you weren’t aware of that sensation before. Along similar lines, have you ever unknowingly cut your finger, but not noticed until you saw that it was bleeding? Undoubtedly, the cut immediately stimulated the nerves that convey pain information to the brain, so why didn’t it hurt? Well, it’s because your brain chose not to attune to that signal, and you didn’t consciously perceive the pain. However, seeing blood was a signal that your brain did not want to ignore, and so it processed the information differently and created a pain output.  

Let’s consider another analogy: Imagine a woman and child are involved in a car accident; the woman breaks both of her wrists, but is somehow able to pry her child from the vehicle without feeling pain. This was possible because her brain was more focused on the impending threat of the situation and did not attune to the pain signals coming from her broken wrists. We hear about these types of scenarios all of the time – people performing seemingly super-human physical feats, despite having just sustained significant injuries. It’s not just adrenaline, it demonstrates the fact that pain only exists when our brain consciously perceives these signals and processes them as pain.

So, why does the brain perceive some stimuli as painful and others as nonpainful? It depends on how much of a threat your brain perceives.  Let’s think of your nervous system as a house alarm. Someone breaks into your home in the middle of the night and it triggers the alarm. You call the police and the intruder is taken to jail; you repair the window that was broken and try to move on. Some people can move and forget about the intrusion, while others have a harder time with this.  If fear persists, whenever someone walks across your lawn you’ll want to trigger the alarm. Your alarm system has become “sensitized” and this is exactly what can happen to your nervous system after an injury.  

Now that you understand pain a bit more, I want to introduce the concepts of acute pain versus chronic pain. Acute pain is what we experience immediately following an injury; it’s typically due to inflammatory processes that ultimately lead to healing. Now, we know that in most circumstances (e.g. in the absence of a diseased state), the body will heal itself within 3 months.

Chronic pain on the other hand, is conventionally defined as pain that lasts for more than 3 months. In these cases, we know that the sensitivity of our nervous system is typically to blame for the persistence of pain, as tissues should be healed by this time. It’s also very important to note that chronic pain may develop without any injury! In these situations, there were typically multiple factors stimulating the alarm system and leading to sensitization (e.g. hormonal imbalances, emotions, stress, minor infections and even nutritional status).

So naturally, we must ask – what leads to centralization of the nervous system?

We have over 400 nerves in our bodies. They are constantly being stimulated and conveying information to our brains. These nerves can be stimulated by temperature changes, stress, changes in blood flow, movement and immune responses. When someone with a sensitized nervous system experiences nerve stimulation from something like cold, their brain may actually experience this as pain. The same thing can happen when nerves are stimulated by stress, movement and immune responses, even though those things aren’t actually conveying information due to tissue injury.

I like to compare our pain threshold to a bucket of water. Let’s say that when your bucket overflows, you experience pain. Any stimulus (e.g. cold temperature, stress, movement, inflammation) fills your bucket. So what happens when your bucket is sitting at 90% full all of the time? In those cases, something as innocuous as movement can cause your bucket to overflow and lead to a pain experience, even though no tissue damage occurred.

Now, that’s not to say that chronic pain is “in your head.” It most certainly has a physiologic basis. Studies have shown that with repeated pain signaling, there are changes at the level of the spinal cord, namely an increase in receptors that receive and respond to incoming pain signals. There are similar changes in the brain. There is an area in the brain referred to as the sensory homunculus, which essentially is a map of the body. There’s more area devoted to the hand, which makes sense because our hand is much more sensitive than our forearm or elbow. However, with repeated stimulation, there is “smudging” of this map, and when this happens stimulation of another part of the body may be perceived as pain in an adjacent area. Notice that your foot is located near your genitals on the map. When someone experiences chronic pelvic pain and has “smudging” of their map, they may experience pelvic pain with any sort of stimulation of the feet or toes.

Source: https://commons.wikimedia.org/wiki/File:1421_Sensory_Homunculus.jpg

That being said, all of the following can “fill” our bucket and stimulate/sensitize the nervous system:

  • Fear
  • Movement
  • Failed treatment
  • Hormonal imbalance
  • Emotions
  • Stress
  • Minor infections
  • Nutritional status
  • Sleep deprivation
  • Ongoing pain
  • Uncertainty about pain

Pain is clearly complex and has an emotional component. Think about it – we refer to grief or heartbreak as pain, and perceive it as such. That being said, our fear, anxiety and disappointment surrounding physical pain will cause further stimulation of the pain system and perpetuate our pain experience.

The Biopsychosocial Pain Model explains this well. There are psychological, social and biological contributors to our pain experience and affect how we perceive pain.

Pain also depends on context.  As with all sensory information, the brain must perceive the information and then assign meaning to the sensation. The brain’s understanding and processing of pain depends on memory, reasoning and emotion. We also know that a lack of knowledge and understanding enhances fear, which thereby increases pain. And this makes sense – pain can be unpredictable (especially low back or pelvic pain). When we don’t know what to expect, it seems much more threatening, and therefore more painful. 

Consider this – the pain we perceive from cutting our hand tends to subside relatively quickly. This is because we not only know what caused the pain, but we are typically confident that the cut will heal quickly without medical intervention. Let’s take this one step further and assume that someone sustained a cut that required sutures – some people have less pain after they get stitches, arguably because they’re more confident that they will heal. It certainly isn’t because stitches make the cut hurt any less!

What’s more, when we experience pain in more private areas (as is the case in pelvic pain), we are likely reluctant to discuss our pain with others. Whereas, you may be more apt to discuss pain that seems more common. Let’s say, for example that you started experiencing low back pain all of the sudden. You may complain to your coworker that your back started hurting all of the sudden. Perhaps your coworker would share a story where she described similar pain that came and went quickly. Or maybe she’d ask you questions and help you find an explanation for your pain, “Oh, you shoveled snow yesterday! I bet that’s it. Put some heat on it and I bet you’ll be good as new tomorrow.” These stories can offer reassurance and help us to reduce pain. But if you’re experiencing pelvic pain, chances are you won’t be talking openly about it and may not get this encouragement or validation, thereby exacerbating pain.

In my personal experience, fear is the biggest driver of chronic pain. I herniated a disc in my back in 2017, and it took me nearly a year to get the courage to resume heavy weight-lifting. That fear that we experience is protective – it’s a great survival mechanism. But, it can really perpetuate chronic pain. Thoughts also serve as strong stimulus to our nervous system. After all, conscious thoughts are immediately attuned to. We then start to avoid certain movements that likely are safe to resume. And the more we play that dialogue in our head, the more we believe it. If we start to modify the way we move out of fear of pain, that pathway becomes automatic, and the pain experience is perpetuated.

Bottom line: pain and tissue damage are mutually exclusive.  That is, the intensity of pain does not correlate with the amount of tissue damage.   I frequently see patients who show significant disc herniations on MRI, but have no back pain. By the way, this has been demonstrated in research time and time again – the amount of disc/nerve damage does NOT correlate with pain levels. On the other hand, think about how intensely a papercut (a very minor injury) hurts! What we DO know, is that the intensity of chronic pain is dependent upon how many other factors are “filling our bucket.”

That being said, treatment of chronic pain must be multifactorial. Remember, the tissue has likely healed by 3 months, so persistent pain is related to nervous system centralization and not due to tissue injury.

Treatment of chronic pain should incorporate the following:

  • Education: Having an understanding of your pain helps to provide an explanation, alleviate fears and provide you with a sense of control as you pursue a treatment plan.
  • Manual therapy: We know that postural muscles become inhibited when pain is present and larger, global muscles can go into spasm to try and protect you. Therefore, seeing a physical therapist for manual work can help to relax muscle, bring blood flow to areas and help to restore function to those smaller, postural muscles. Manual therapy can also address scar tissue, which can absolutely contribute to pain by decreasing blood flow, entrapping nerves and limiting soft tissue mobility.
  • Corrective exercise: A skilled physical therapist can assign you appropriate corrective exercises to address tight muscles and to promote the strength of muscles that may be inhibited or weak, which can facilitate pain-free movement.
  • Aerobic exercise: Getting just 20 minutes of aerobic exercise per day (with a goal of elevating your resting heart rate by 20 beats per minute) can significantly reduce your pain.
  • Improve your posture:  Finding a more appropriate posture can lessen the load on your joints, prevent muscle tension and help promote appropriate blood flow to all of your nerves.
  • Stress management: Persistent activation of the sympathetic nervous system and the hypothalamic-pituitary-adrenal axis occurs with persistent high stress levels; and when this happens, tissue healing is impaired and sensitivity of tissues is increased.
  • Breathing: Not only does deep breathing help to move blood and deliver more oxygen to your tissues, it can also lessen the threats of any incoming stimuli to your nervous system.
  • Sleep: We know that our bodies need sleep to heal, but our nervous system absolutely requires sleep in order to function appropriately. If you are sleep deprived, you will wake up with a bucket that is fuller than it ought to be! I encourage all of my clients to focus on not just the quantity of sleep, but also the quality. Establishing a night-time regimen that helps to down-regulate the nervous system is absolutely essential to falling asleep and staying asleep.
  • Nutrition: Nutrient deficiencies can impair healing, perpetuate muscle spasms and can also affect the way our nervous system functions. Furthermore, eating inflammatory foods leads to additional nerve stimulation, which can perpetuate the pain response.
  • Hydration: Studies have shown that achieving appropriate electrolyte balance and hydration status is beneficial in reducing muscle tension and trigger points, which can help to control pain.
  • Ensure adequate social support: Research has shown that having psychological support and social connections are correlated with improved outcomes when it comes to chronic pain. And that’s no surprise – chronic pain can be very draining; having someone to talk to about your pain can help you cope and deal with negative emotions associated with your pain experience.

As you can see, chronic pain is very complex and causes very real changes in your body. However, many physical therapists are well-equipped to help you navigate your healing journey. Be sure to find a provider who takes an integrative approach and focuses on all facets of your life, because pain truly involves multiple systems. And more than anything, remain hopeful! I have worked with many people who have found relief and healing, and I’m confident that you can do the same.

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