Pain can be mysterious, especially persistent pain. Virtually everyone knows what pain feels like. But do we understand what pain really is and how it comes about? With pain, knowledge is power. Here are three definitions that I have found helpful to better understand this seeming mystery of the human body:


“Pain is a decision by the brain, based on everything it knows about the threatening situation.”


This definition comes from the book Why Do I Hurt? by top pain researcher and educator Dr. Adriaan Louw. Why do I hurt? is a patient handbook for better understanding their persistent pain. It was an immense help to me as a chronic pain patient, and now I continue to return to it as a practitioner for clear and easy ways of teaching patients about their pain. I like the simplicity and clarity of this definition as well as how concisely it debunks two major myths about pain.

The first is the idea that pain is a sensation that comes from the peripheral nerves of the body: people often believe there is a nerve that conducts messages of pain that are then “read” by the brain. The reality is that the message of pain is written in the brain, and the peripheral nerves can only send messages regarding sensations and chemicals that have passed a certain threshold.

The other myth our society tends to perpetuate around pain is that it is directly related to an actual amount of tissue damage or some kind of anatomical abnormality. However, the last four decades of research have demonstrated that several inputs affect whether or not we will feel pain, including something as seemingly unrelated as memory. (An entertaining TED talk by Lorimer Moseley illustrates this more in depth). This is why you can have two people with similar imaging results who have vastly different pain reports. Tissue damage still plays a significant role, but it’s not the only factor in how a person develops pain, and thus treating persistent pain often requires more than simply treating the tissue damage.


“An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.”


This is the definition of pain from the International Association for the Study of Pain (IASP). Many expert voices went into creating this definition. I appreciate that it recognizes that pain is an emotional experience. Pain, by virtue of being unpleasant, is always emotional, and to effectively treat pain, we must recognize that there is an emotional toll which will effect physical treatment. The toll may be different for everyone, but it exists nonetheless.

Another advantage of this definition is that it recognizes the variance in tissue damage that can be associated with pain, even to the point of tissue damage being only a possibility. One of pain’s main purposes is to protect us by getting us to stop doing something that is actively causing or could cause damage. But one of the ways our nervous system determines what may cause tissue damage is our beliefs, and these can sometimes be mistaken. For example, a person with low back pain may be forever afraid to twist because a friend with low back pain got injured while twisting. They have a strongly held belief that such movement will cause harm, and the movement causes them a very real pain as protection because of that belief. Yet a thorough evaluation of the person’s situation may reveal that twisting really won’t cause any kind of tissue damage to their back, and it may in fact provide many benefits.

Sometimes the belief of potential harm is necessary and reasonable, but there are many times when such beliefs are misguided. Yet they are still enough to provoke a pain response! A physical therapist is uniquely qualified to help a patient discern whether their pain is based only on overly protective beliefs or if the movement is truly damaging and ought to be avoided or modified. We enjoy when we are able to empower a person to move in ways they previously thought were off limits or to help them modify movements that are painful.


“Pain is a mutually recognizable somatic experience that reflects a person’s apprehension of threat to their bodily or existential integrity.”


This was proposed by three Australian researchers as a revision to the IASP definition. While it’s important to recognize the good of the current IASP definition, I admittedly prefer aspects of this revision. A large reason for that is its phenomenological approach; it draws even greater attention to pain as a holistic experience than the current IASP definition does. I especially prefer the use of the phrase “threat to their bodily or existential integrity,” rather than referring only to tissue damage. This speaks to the reality of a type of pain that is near and dear to my heart: pain that is felt in the body, seen in tight muscles or movement restrictions, but is associated primarily with feeling threat to one’s emotional and psychological well-being.

People can actually develop pain without any sort of physical injury, from the common headache after a stressful day to debilitating pelvic pain after sexual trauma. (Not all headaches or pelvic pains are related to psychological trauma, of course, which makes it all the more important to be evaluated by a skilled clinician when there is persistent pain to achieve a proper diagnosis). This is because they have experienced a very real threat. The human nervous system is wired to protect not only our physical tissues, but our emotional well-being, too. Even people with injury-related pain commonly report an increase in sensitivity after episodes of emotional stress. As the medical community increasingly moves toward holistic, integrated, biopsychosocial, and patient-centered philosophies, I believe this definition of pain and others like it will become a critical perspective in effective diagnosis and treatment.


This article is intended for educational purposes only and should not be taken as medical advice or treatment.


Cohen, M., Quintner, J., & Van Rysewyk, S. (2018, March/April). Reconsidering the International Association for the Study… : PAIN Reports. Retrieved November 27, 2018, from

IASP Terminology. (2017, December 14). Retrieved November 27, 2018, from

Louw, A. (2013). Why do I hurt?: A patient book about the neuroscience of pain. Minneapolis, MN: Orthopedic Physical Therapy Products.

Image credit: Public domain image “Man Thinking” from Pixabay user photosforyou.