I started writing this blog post with the intent of providing a brief explanation of pain. However, the complexity of this topic has caused this short post to evolve into a lengthy article which I will post in two parts. The first part will discuss acute pain (pain lasting for less than 3 months) and chronic pain. I hope these posts are enlightening and allow you to better understand how pain works and how you can take control of your pain.
Pain is defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage.1,4 It is a very complex emotional experience consisting of both physical and psychological aspects. Pain plays a very important role in the body when it serves as a warning that there is a problem.3 In essence, it should function as our check engine light to let us know something is wrong so we can intervene and protect our bodies from further harm. Like the check engine light in your car, pain mainly functions to tell you there is a problem. It does not necessarily tell you the exact location or cause of pain. To determine the exact cause of the pain and change the factors contributing to pain one must have a thorough understanding of pain.
Pain can be categorized in many ways, although the two most common categories include acute pain and chronic pain. Pain lasting less than 6 months is characterized as acute pain, and pain lasting longer than the time required for normal tissue healing (greater than 6 months) is characterized as chronic pain.1,2 Acute pain generally occurs due to actual or potential tissue damage whereas chronic pain can be due to neurological or psychological changes. Acute pain functions to help us identify which activities are potentially harmful to our bodies so we can avoid or modify those activities. Sometimes, however, even when pain is acute it is still difficult to understand which activities are provoking pain and which tissues are being affected.
There are many reasons pinpointing painful activities or identifying affected tissues can be difficult even with acute pain. In the following paragraphs we will discuss some of the reasons pain is so complex and why it can be hard to treat. First, many tissues throughout the body (bone, ligaments, tendons, muscles, fascia, internal organs, and joint capsules) contain pain receptors or nociceptors. This means that any of these anatomical structures can send signals to your brain that may be interpreted as pain. It is important to note, pain in some tissues is easier to pinpoint than in others.1 For example, pain coming from skin is much easier to localize than pain coming from muscles.1,2
In general, pain arising from muscle and fascia is not very well localized. This means that not only is it difficult to determine the part of the muscle / fascia that is problematic, but pain may not even be coming from the area in which pain is felt. In some cases muscles / fascia will refer pain to a region distant to the site of the problem. 2 For example, tissue overload in the soleus (calf) muscle resulting in the development of a myofascial trigger point can cause pain in the sacroiliac region of the low back. This is similar to the phenomenon where patients can experience left shoulder or jaw pain when they are experiencing a heart attack.
Now let’s apply these principles to a real life patient example. Even something as seemingly straightforward as knee pain may not be a cut and dry case even when patients have undergone diagnostic imaging. Don’t get me wrong: X-rays and MRI’s as well as the quality of pain (sharp, dull, aching, and throbbing) can provide clues as to the tissue or tissues responsible for pain but should not be used as the primary diagnostic criteria. Even when an x-ray demonstrates arthritis, aching pain in the knee may be caused by the joint capsule surrounding the knee, the quadriceps muscle, the adductor muscle group, bursa, or the infra-patellar fat pad. Since this is the case a thorough examination must be performed to identify the tissue or tissues at fault in order to address the problem and correct the source of pain.
With this example, hopefully you can begin to see how much of a puzzle pain can be for patients and clinicians alike. If clinicians do not correctly identify and address the tissue or tissues at fault, pain will persist and patients may have to rely on medications for pain management. At this point, the puzzle I’ve described solely has to do with acute pain or pain lasting less than 3 months. This puzzle can be further complicated when pain becomes chronic or lasts for longer than expected for normal tissue healing. In part two of this blog post we will provide a brief overview of chronic pain and discuss what steps can be taken to address this pain.
- Cameron, Michelle H. Physical agents in rehabilitation: from research to practice. Elsevier Health Sciences, 2012.
- Mense, Siegfried. “Muscle pain: mechanisms and clinical significance.” Dtsch Arztebl Int12 (2008): 214-9.
- Melzack, Ronald. “Pain and the neuromatrix in the brain.” Journal of dental education12 (2001): 1378-1382.
- Moseley, G. L. “A pain neuromatrix approach to patients with chronic pain.” Manual therapy3 (2003): 130-140.