We live in an incredibly visually dependent society. Medicine has trained both doctors and patients alike to rely heavily on imaging, and visual examinations to obtain a diagnosis. The push towards telehealth medical care has reinforced these evaluation strategies even more. While most doctors also run other tests such as a variety of labs, listening to your heart/lungs, and feeling your pulse, the testing is not all inclusive. Any honest physician would agree, that we are constantly learning new things about medicine and the human body. There are diseases that we couldn't test for 100 years ago, that we have since been able to identify and develop tools to diagnose today.
As a result, many patients come to their physical therapists' office frustrated that they are in pain, and their physician has told them that nothing is wrong on their imaging. While most people don't undergo testing hoping for something to be wrong, they are usually hoping that something will be found that justifies and explains their symptoms. Ideally, the doctors will find something that can be easily fixed.
If all of the tests come back negative, patients are often confused. They believe that must be some kind of mistake. When the pain they experience is so significant and persistent, surely, something must be wrong.
To answer the question of why doctors can't see pain, we have to first understand that no one can really see pain at all. While almost every human being can say they've experienced the sensation of pain in one form or another, it isn't a sense that we experience through our eyes. While there can be signs of damage to our bodies that we associate with pain on the outside, that isn't all of pain. The experience of pain actually happens inside of our bodies.
Pain is complicated, and verbal language has a hard time describing just how complex pain is. For example, if you were to
Burn your hand on the oven rack
Step on a Lego
Prick your finger on a sewing needle
Stub your toe
Shock yourself on a loose electrical wire
All of those things could be described as "painful". They do not however, all feel the same. The pain from a burn is different than the sharpness of a sewing needle, or the tingling pain that shoots through your nerves from the loose electrical wire. To make it more complicated, some of these painful experiences leave physical signs of injury like a burn on your hand, while others like an electrical shock may not be visible at all.
The truth is that we are better off thinking of pain like a "sixth sense" if you will, rather than trying to make it fit into a box of one of our other senses. In fact, pain can touch all of our other senses. If a sound is loud enough, it becomes painful. If a coffee cup is hot enough, it burns your hand and becomes painful. If the light is bright enough after walking out of a dark movie theater, we say that it "hurts my eyes".
A pain signal in your body is better described as your body's way of saying "That's too much!" of another sense, and usually signals your body's belief "That's so much that it's dangerous."
So how do doctors test your Much-ness Meter? Doctors and scientists run studies where they perform the same test on a large number of people to decide what is considered to be normal. Doctors then use those studies to compare your body to other people who are considered normal or average. For example, we know that the average person will experience pain if they have a broken ankle. We can see broken ankles on an x-ray, and so we use imaging as a test to explain a person's pain. That does not mean however that everyone with a broken ankle will have pain. For example, if the nerves in the spinal cord are damaged, a person may be unable to feel their legs and therefore won't have pain even though their ankle is broken.
Unfortunately, many of us don't fit into the "average" category in one way or another for a variety of reasons. Have you ever noticed that some people can tolerate spicy food better than others? Or perhaps you know that some people are more easily startled by loud noises? How about the fact that one person can pick up a hot bowl out of the microwave while another person cannot without feeling they burned their hand? The fancy term for this is medicine is a threshold. There are entire scientific studies dedicated to assessing what is called a pain pressure threshold in different populations of people.
Receiving a diagnosis of fibromyalgia according to the American College of Rheumatology's 1990 diagnosis criteria is largely dependent on having a pain pressure threshold that is low enough that a pain response is triggered if certain points on the body are touched with 3lbs of pressure. While a new diagnosis criteria was proposed in 2010 (proof that medicine does attempt to learn and improve over time), the 1990 criteria is a good example of just how limited the medical field truly is in it's ability to assess pain. Doctors are entirely dependent on the patient to report to them whether the pressure applied is painful or not. It is not an objective test like an x-ray which either shows a break in a bone or it doesn't. It is what we would call a subjective test that is dependent on the individual to self report their experience. (1)
The medical community is still learning how pain is processed in your body. While we believe that pain is processed in your nervous system, admittedly, it is one of the systems in your body we know the least about. (See The Nervous System Whisperer: Where does pain come from?)
The electrical shock from a loose wire is a good example of why your doctor cannot see your pain. Your nervous system communicates messages in your body with electricity. Think of your nervous system like the wiring in your house. If you were to take a picture of the wiring in your house and show it to your electrician, it would have limited value. While they may be able to see if a wire had been completely crushed, or disconnected, the photo would not tell them much about what the wires in your house do. In order to see that, an electrician would use a different tool to assess electrical current in the wires. They would have to problem solve and test in multiple places, to determine if the problem with your wires was happening locally by the outlet that isn't working, at the breaker to see if you've blown a fuse, and perhaps even outdoors in the wires that lead to your home from the power company.
Processing pain in your nervous system works the similarly, but is even more complicated. The wires in your house don't send as many kinds of messages as your nerves do, and the human brain that is the boss of the nervous system is not as well understood as your local power plant. (See: How Nerves Work: Simplifying Complex Neuroscience)
In summary, just because your doctor cannot see your pain, does not mean that your experience of pain is not real. In fact, one of the best analogies to help doctors and patients understand pain is the simplest one. Every medical student at some point watches a video on standard precautions to prevent the spread of infections. The typically dated looking video usually shows a person doing the wrong thing like touching a wound without gloves, or a simple cough into their hands. A green blob to symbolize germs then spreads onto their hands. The person will then touch something in the hospital like a phone or a door handle before they wash their hands and the infamous green blob will spread. Then someone else comes along and touches the same door handle unaware of the germs present there. That person touches a few more things and before you know it, the whole hospital is covered in green blobs because the germs have spread everywhere.
The truth is that pain, like germs, is an invisible illness, but that does not mean that it is not real. Most doctors would say that they believe that germs existed before we were able to see them on a microscope. They didn't miraculously appear for the first time when we developed the technology to be able to see them. My encouragement to patients and providers alike is that pain is the invisible disease of our day. While medicine's ability to objectively test for pain at this point in time is limited, that does not mean that pain is not real.
This article is intended for educational purposes. In light of the fact that pain is processed in the brain and every person's brain and nervous system are unique, this article is not intended as a replacement for individual medical advice. If you are looking for support in living life with chronic pain and are interested in physical therapy services to evaluate your case individually, click Book Online above to schedule an appointment.
(1) Due to the subjectivity of this testing, it must be acknowledged that while many patients who report pain are honest, some individuals may report pain that are disingenuous and medical professionals may appropriately exercise caution in relying solely on subjective symptom reports when making a diagnosis in individual cases.