Acute versus Chronic Pain: Understanding the difference and choosing appropriate treatment

Pain is a human experience. It can be uncomfortable, with the potential to be horrible. The commonly accepted definition of pain from the International Association for the Study of Pain, states that pain is “an unpleasant sensory and emotional experience, associated with actual or potential tissue damage…”. Since pain is an individual’s experience, we should start any discussion of acute versus chronic pain with the understanding that defining and describing pain in an adequate manner is very difficult.

Pain can be categorized in many ways, including the differentiation of acute from chronic pain. Knowing differences in acute and chronic pain is important to both health care professionals and patients. The best treatment outcomes are most probable given the ability to adequately compare and contrast the two. However, this is not a simple task. Even the IASP website does not include definitions of acute and chronic pain in its taxonomy.

In the past, acute pain was believed to be directly associated with tissue injury. The intensity and location of the pain were considered to be an accurate reflection of the tissue problem. Chronic pain, on the other hand, was considered to be pain that lasted longer than normal tissue healing time. Its intensity and location were considered inaccurate reflections of tissue injury. Acute pain was stated to have a sharp quality while chronic pain was said to be dull. Unfortunately these incomplete and inaccurate thoughts about acute and chronic pain have persisted even though they are not supported by current scientific understanding.

Acute pain has been defined as pain with a duration of less than 2-3 months, while chronic pain has a duration of longer than 6 months. Durations between three and six months are classified as sub-acute. Since the belief has been that pain relates directly to tissue health and most tissue injuries resolve in 2-3 months, it was believed that pain should also resolve in that same time. However, many other factors impact whether pain persists. A broader understanding of pain is required in order to stop making inaccurate links between pain and tissue damage.

In order to understand acute and chronic pain better, it is helpful to know three important things about pain.

  • Pain is an output of our brain.
  • Pain is produced to protect us.
  • The longer we experience ‘uncontrolled’ pain, the more sensitive the pain system becomes.

Whenever we feel pain, our brain has already decided that something dangerous is happening and that protective action is necessary. When pain persists, the systems learn to protect us more. The nervous systems become wound-up. The nerves fire more easily than ever before, sending greater volume of signals to the brain, which in turn is interpreting everything from a state of hypervigilance.

Based on information from pain science we could describe acute pain as:

  • an adaptive response(s) of the organism’s protective systems,
  • in which the experience of pain motivates the individual to consciously perform protective actions that promote healing and recovery,
  • and in which the autonomic responses of the organism promote healing and recovery.

In other words, in acute pain, the pain is serving an adaptive purpose. It is motivating us to make decisions and take actions that will keep us from reinjury and help our tissues heal. It is also creating a situation inside the body whereby physiological processes are promoting healing and creating positive adaptation to the pain.

Chronic pain then could be described as follows:

  • maladaptive responses of the organism’s protective systems,
  • in which the experience of pain motivates the individual to consciously perform protective actions that limit recovery,
  • and in which the automatic responses of the organism also limit recovery.

In other words, the pain is no longer protecting us from imminent danger. The protective systems are providing an experience of something very dangerous occurring, right now, in the body. This produces a state of stress in the individual and in their physiology, and this stress reinforces the hypersensitive responses that in turn limit recovery.

Chronic pain does not mean that there is nothing wrong. Something within the body’s anatomy or physiology has produced pain. Then for reasons we do not fully understand (due to the complexity of the pain systems and of human experience), the organism’s pain systems have not responded in the typical manner. Usually, as time passes and no matter how horrible the initial injury, the pain systems will adapt by becoming less responsive to signals from the injured tissues. In chronic pain, this positive adaptation does not occur. As time passes, the pain systems become more sensitive, hyper- responsive and able to produce intense, spreading, unremitting pain.

Acute pain and chronic pain also differ in effective treatment practices. Acute pain often resolves on its own, while chronic pain does not. People with acute pain can often be treated effectively in primary care, based on the health professional’s knowledge of pathophysiology and tissue healing. People with chronic pain typically require more specialized knowledge from the health care professional, and often require treatment from a team of health care professionals. Chronic pain also necessitates treatment of the hypersensitive nervous systems, based on our understanding of pain neuroscience, a biopsychosocial perspective, and on neuroplasticity.

One key similarity between acute and chronic pain is that both require adequate pain relief. Uncontrolled pain magnifies pain, as well as all of its detrimental effects, no matter how much we try to suppress it. Within days of any injury, the acute pain should start to decrease. If it does not, or if the pain is creating a substantially negative impact on function and life, services such as acute physiotherapy will be beneficial. Seeking care is better than being tough in the face of uncontrolled pain. Routine acute physiotherapy services include hands-on treatments, exercises, intramuscular stimulation, and acupuncture. When routine acute pain services do not successfully decrease pain and improve function, then more complex, interdisciplinary treatment is required. Although it is not possible to definitively state when chronic pain services should begin, these should be considered as early as one month after an injury when there has been no improvement, and as early as three months when routine medications or other acute pain services are not providing the expected benefits. People with chronic pain require adequate pain relief too, however they also require interventions specific to chronic pain – pain education, goal setting, self-regulation and stress management, medication and psychological counselling, and occupational therapy services.

A simple truth about chronic pain is this – the presence of chronic pain implies changes well beyond the tissue injury. Effective treatment of all pain typically requires specialized knowledge, whereas chronic pain requires a team approach and interventions for the body, mind and spirit.

By Neil Pearson © 2012

Neil Pearson works clinically in Penticton, BC, Canada providing the knowledge and tools for effective pain self management throughout physiotherapy and therapeutic yoga. He is founder and director of Neil Pearson Physiotherapist Corporation, which operates as “life is now”™. He is a regular contributor to OrionHealth’s staff education. More on Neil’s work can be found on his website at

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