Sharp, dull, achy, burning, radiating, shooting these are just some of the ways patient’s have described their pain to me. Pain is one of the main reasons why patient’s come to see us. Whether from an acute injury, a surgery or something that came out of the blue, pain is often what drives us to seek help! Pain is actually a good thing! It grabs our attention and warns us of an actual or potential threat to our body’s tissues, helping to protect us from further damage. However, sometimes our body’s alarm system doesn’t stop ringing the alarm even after source of harm is gone. What is happening when our tissues have healed, our injuries have repaired but the pain has not?
Chronic pain is defined as any pain that lasts greater than 3 months (1)(2). This is the amount of time that it takes tissue form an acute injury to heal. To understand chronic pain we must first understand how we perceive pain.
Throughout our body we have sensory nerves which respond to external stimuli such as mechanical (pressure), temperature and chemical changes (1)(2). There are no specific “pain sensitive” nerves or nerves that send a “pain signal”(1). Instead, there are specialized nerves which respond to any stimuli which can be considered harmful or dangerous to our tissue(1). The detection of what we call a noxious stimulus is known as nociception and these nerves have been aptly named nociceptors(1).
A nociceptor carries that danger signal to the spinal cord where it releases a chemical response (2). Many nociceptors and other sensory nerves can synapse on to one receptor in the spinal cord(2). The spinal cord itself plays a role in interpreting the severity of a signal. If enough nociceptors are activated and a critical threshold of stimulus is reached, the spinal cord transmits a danger signal to the brain (2). It is then the brain’s job to interpret the noxious stimulus, as well any other inputs your body may be providing (1). If your brain deems your tissue to be in danger or potential danger it warns you with the sensation of pain (1).
Chronic pain occurs when there is a sensitization of this pathway from the tissues to the brain. There can be both peripheral and central sensitization (central refers to the processing centres of the spinal cord and the brain) (1). In response to persistent pain in damaged and weak tissues, the receptors in the tissue, spinal cord and brain adapt to become better at perceiving and interpreting these noxious stimuli (1). As a result, stimuli that wouldn’t normally hurt become painful, and the intensity of a painful stimulus is enhanced – this is known as allodynia and hyperalgesia respectively (1). The brain then interprets these signals to mean there is more danger or harm being done to the tissues then there actually is and you in turn experience more pain (1).
Pain and in turn chronic pain, is multifactorial (2). Not only can a sensitized nervous system affect how you perceive pain but your emotional well-being and your thoughts and beliefs about pain can also influence your pain experience (4). An encounter with a stimuli that was previously perceived to be painful can provoke a sense of fear or anxiety in someone (4). These feelings can have a direct effect on our physiology, increasing the production of cortisol and other stress hormones which can themselves lead to sensitization of our peripheral and central nervous system (4).
So how do we treat something as complex as chronic pain? With a multi-factoral approach! A physiotherapist will work to de-sensitize the nervous system. This may include releasing tight muscles, strengthening weak muscles and improving neural mobility. We promote graduated return to pain free movement of the affected area, which helps to re-program our sensitized nervous system. The brain learns that not all movement is painful, minimizing fear and anxiety associated with movement and reducing the level of stress hormones sensitizing the system. Treatment may also include such tools as mindfulness, meditation and body mapping to help patients gain control of their negative thoughts and beliefs about their body and the pain they are experiencing.
The research behind pain science continues to grow and we learn more about managing chronic pain every day. If you suffer from chronic pain, contact us to book an assessment with one of our physiotherapists today!
Written By: Tiffaney Marlow – Physiotherapist
1) Butler, D. Moseley L. (2003) Explain Pain. Adelaide, Australia: NOIgroup Productions
2) Eds. S. Rashiq, D. Schlopflocher, P Taenzer, E. Jonsson. (2008) Chronic Pain: a Health Policy Perspective. Weinheim, Germany: Wiley-Blackwell
3) Marchand S. (2014) Neurophysiology of Pain. Mental Health and Pain: 15-31
4) Linton S., Shaw W. (2011) Impact of Psychological Factors In The Experience of Pain. Physical Therapy. 91(5)