Chronic Pain is defined as experiencing pain for a period of 3 months or longer. Chronic pain is something we see here everyday in the clinic. It can be exceedingly difficult to treat at times, but also very rewarding if we can help someone get out of chronic pain. Like anything in life that requires a lot of work, sweat, and tears, the payoff is usually worth the effort.
Chronic pain, however, requires a different approach than most musculoskeletal injuries we encounter. This is because the mind plays such an important role in how we perceive chronic pain. All pain, believe it or not, comes from our mind. We have certain receptors that detect pain called nocioceptors. Technically, all these receptors do is detect a change in sensation that is then transferred to the brain to be deciphered as a threat or not. If the brain decides this input is a threat, then it classifies it as pain.
Now there are two types of axons that are attached to these pain receptors, the A delta fiber and the C fiber. The A delta fiber detects extremely significant sharp pain, and is able to send signals very quickly to the brain. This would be the type of pain felt by a pin prick or getting a finger stuck in the door. The C fiber detects changes in tissue that may cause acute damage, but not of the extreme importance as the A delta fibers. This would be more like the pain felt in a swollen joint, overstretched muscle, or healing bone fracture.
What can happen with C fibers is they will increase their sensitivity to pain if the neurons are repeatedly fired. This can be what happens with chronic pain. When someone has been experiencing pain for extended lengths of time these receptors can become highly over-sensitized, often to the point where even the thought of doing a certain activity will trigger a painful response. This is where chronic pain becomes increasingly hard to treat. At this point, we are more treating the “threat” of pain versus actual tissue damage. Many times, by this point, the tissue may be completely healed from the initial damage, but our mind still views the area as a “painful” place.
It really all comes down to the “threat”, or the interpretation of the “threat”, of pain. For example, in therapy a common diagnosis we will see is shoulder impingement syndrome. For many individuals it can become so intense that they will no longer lift their arm due to the threat of pain. In this case, the first step in rehabbing the shoulder would be to teach the individual to lift the arm without actively using the arm, but doing it more “passively”. “Passively” means they use their good arm to help lift their injured arm with the help of a stick or a pulley. That way their mind has a chance to process the fact that it doesn’t always hurt to lift their arm, in fact there are ways to lift the arm without it hurting nearly at all. This then allows the brain to “de-threaten” the movement of their arm, and allows the C-fiber receptors to become less sensitive. In time, the painful shoulder will be able to work on its own without the threat of pain.
So anyway, that is a little glimpse into the complexity of chronic pain and why treating the mind in this case can be even more important than treating the body!