by Dr Nathan Pierce, DPT, OCS.
Have low back pain?
Did you know that 80% of the population will experience lower back pain in their lifetime? 85% of low back pain is non-specific meaning that the cause is not clear. How can that be? Oftentimes this is because pain is equated with tissue damage.
Pain doesn’t always equal tissue damage. In fact, pain is not a sensation at all. The term “pain fiber” is misleading as they do not exist. What we do have are nociceptors. Nociceptors are tiny nerve fibers located within our skin, soft tissue, bones, blood vessels, nerves and organs that detect danger. They are activated and relay information to your central nervous system under certain circumstances. A “danger detector” is a more appropriate name.
We have multiple different receptor types in our musculoskeletal system that relay information to our brain for processing about our overall “status.” These include those which detect temperature (hot/cold) light and crude touch, pressure, stretch, vibration, chemicals, joint position sense, muscle length and muscle tension. Notice pain was NOT one of them.
Nociceptors are embedded in every single one of these receptor types.
Imagine you are stretching your hamstring and stretch too far.
If the stretch receptors embedded in your hamstring exceed a threshold that is perceived as dangerous, the nociceptor embedded within the stretch receptor will turn on and immediately send information to the brain letting it know that there is a noxious amount of stretch occurring. This signal terminates in the brain in a very organized fashion and is referred to as being somatotopically organized. Somatotopy means that the sensory information in your periphery (head, trunk and extremities) is mapped in a highly organized and structured fashion in the sensory cortex of your brain. When this “danger” information from the noxious stimulus reaches the sensory cortex, your brain will produce a painful experience. You will “feel pain” in your hamstring but your brain generates this experience, not the hamstring.
Pain can be confusing. Because of our neuroanatomy, an injury to our spine can produce symptoms elsewhere in the body. A weakness or injury to your back can produce lower extremity pain. You’re certain your hip is the issue but when you try to press on it, it feels deeper. You’re likely experiencing somatic referral pain from the lumbar spine. Interestingly enough, you may not experience any back pain at all.
Think of the patient you’re responding to who is experiencing pain in the L upper extremity and neck with complaints of chest tightness and shortness of breath.
There is nothing wrong with their arm or neck but the brain is producing an alarm signal about the cardiac ischemia occurring.
Swelling creates confusion. Swelling from an injury triggers nociceptors to become highly sensitized. Your brain determines that these signals are arising from tissue damage and it will protect you from further injury by preventing you from moving in ranges that could interrupt the healing process. Motions are now painful and “tight.” A brilliant system.
Pain is like a check engine light; it tells you that something is wrong, not necessarily what is wrong.
You’ve likely concluded that pain is complex. There’s more. Our own nervous system, via our thoughts, moods and behavior can amplify our perception of pain or even create pain altogether.
Our central nervous system can self-sensitize via a process called Central Sensitization where previously non-painful stimuli become painful. Central sensitization is associated with many factors including stress, anxiety, depression and poor sleep hygiene. These can contribute to increased pain. If you are in pain and are unsure about what to do, get evaluated. Physical Therapists can determine the source(s) of pain and assist you in managing it.
In summary:
- Pain is NOT a sensation but an out product of the brain 100% of the time.
- Increased levels of pain ≠ increased tissue damage.
- Pain is sometimes an unreliable indicator of tissue damage.
- Pain is complex and may require a multidisciplinary approach including Physical Therapy, Exercise and Medical Management including Behavioral Health Consultation.
Additional Resource:
For a great educational video on pain, search “Understanding Pain In Less Than 5 Minutes” on YouTube.
