Your Back Pain Isn’t In Your Back
Pain is a universal experience, the result of ancient neurologic pathways evolved to keep us safe by alerting us to injury. While pain is universal, however, in practice it is an utterly personal experience: none of us can feel another’s pain, we can only guess. A constant in our lives, pain is deeply enigmatic: impossible to describe, difficult to measure, and a vexation for researchers.
Pain can be as simple as stubbing your toe: you know it’s going to hurt, and a moment later it does. In this pause, pain receptors (nociceptors) in your toe send information through nerves (largely myelinated C-fibers) to your spinal cord and then on to your brain where these nerve impulses are interpreted as “pain”. If the injury is trivial, the sensation of pain gradually decreases, and you get on with your day. If the injury is more serious, say, a broken toe, the pain continues until your toe bone is healed and ready to go back into service; only then does the pain subside. We don’t’ often think of it, but pain thus serves two important functions: it lets us know when we are injured, and just as importantly, it lets us know when we have repaired ourselves.
While the pain alert system works with most injuries, there are exceptions. Every burn surgeon knows that a painless burn has a much worse prognosis, because the lack of pain is a sign that the burn is so deep that it has destroyed the skin completely, leaving no functioning nerve endings to report the damage to the brain.
And pain doesn’t only reflect injury. It can also serve as a sort of generalized malfunction signal. So, for example, a cramped muscle can be excruciating, but quickly resets to normal with a bit of massage or walking. A headache too is painful, but usually passes without incident, resetting the pain system.
The disparate examples above suggest that “pain” is a very inclusive term, covering events that are really quite different in their origins and in their implications. It seems the word “pain” is at its root a sort of linguistic workaround, gathering together quite different events for ease of communication.
But there’s actually much more to the story of pain than the simple examples above suggest. Consider this: In the sixteenth-century warfare was made more terrible by the advent of firearms, and soldiers began returning from battle with shattered limbs. The barber-surgeons of the day found that the only way to prevent the slow agonizing death from gangrene was early amputation. And so, they worked to perfect the amputation procedure, which had to be performed quickly because anesthesia would not be invented for another 200 years. It was in this context that the most renowned of the barber-surgeons of this era, Ambroise Pare, made a startling observation: many patients reported continued, agonizing pain in the limb which had been removed, so called phantom limb pain (faux sentiments). Pare speculated that the severed nerves somehow retired back to the brain, bringing the sensation of ongoing pain with them. Rene Descartes, a near contemporary of Pare, disagreed, and believed that phantom limb pain supported his view that “… There is no sensation save that which takes place in the brain”. For Descartes nerves only delivered information; it was the brain that created the actual message, such as the sensation of pain.
It happened that Descartes was right, but phantom limb pain remained an enigma for centuries: how was it possible for an absent limb to cause pain? And how could physicians possibly treat pain in a limb that wasn’t there? It’s a fascinating tale, and it turns out that while pain-relieving drugs were of little help to those suffering from phantom limb pain, treatment using clever “mirror boxes” sometimes succeeded1. These devices momentarily tricked the brain into thinking the body’s missing limb has been restored and thus somehow reset the brain’s expectations, disrupting a pain loop that had been running in the brain, sometimes for decades.
The conundrum of phantom limb pain brings into focus the distinction between acute and chronic pain. Acute pain is the far simpler problem, and is the algorithm the body usually follows. However, sometimes there can be an ongoing source of pain, say a painful arthritic knee, and the acute pain of the boney surfaces of the tibia and fibula continues without resolution and so is termed “chronic”.
The most interesting outcome, however, is when pain persists even when the original cause of the pain has resolved as with phantom limb pain. It is this version of chronic pain that is the most challenging for patients to endure and for physicians to treat, because the source of the pain is the brain.
Back pain can fall into either the acute or the chronic pain category, or even into both categories simultaneously because physicians increasingly think of back pain as a chronic condition that waxes and wanes. Yes, back pain starts as a single incident, but if the circumstances that caused the index event aren’t addressed further episodes of back pain are likely, until a pattern is established that can be difficult to escape.
And, unfortunately, the chronic back pain loop is extremely common. Over 8% of Americans have chronic back pain severe enough that it that limits their activity, imposing an immense burden of suffering as well as an outsized cost for our health care system: back pain is estimated to cost over $100 billion each year in medical care costs alone; lost productivity adds to this cost.
But the news isn’t all bad, because while most Americans have at least one episode of back pain, most do not go on to develop chronic back pain. And it’s possible to avoid back pain altogether by developing movement patterns and habits early in life that keep one’s back healthy and flexible. Children come into the world with perfect posture and we should support their natural inclination. Allowing children to sit less and to sit for shorter periods will obviously help. And when sitting is necessary, allowing children to move rather than sit rigidly can also help. A variety of alternatives to standard chairs that allow “active sitting” are now appearing in classrooms, and although the scientific evidence is still thin it’s likely that more creative sitting options will pay benefits beyond better posture and less back pain2: allowing movement can help kids with ADHD focus, and may actually help all kids to concentrate better. And active sitting alternatives need not be expensive; some are almost free (buttonchairs.org).
For adults who already have back pain, minimizing prolonged fixed postures and activities that are known to trigger back pain are an obvious place to start. But adopting postures and movement patterns that allow the back to function gracefully may avoid back pain episodes altogether. It’s alarming that 80% of Americans have back pain that sends them to a health care professional sometime in their lives, but this also means that 20% of us never have a problem with our backs. How do these fortunate few do it? We don’t know for sure, but adopting postural habits that keep our backs strong and supple is certainly part of the picture.
Which posture is the best posture for avoiding back pain? That’s a question for another blog. Or two.
1Mirror Therapy for Phantom Limb Pain
2Active sitting – could we give our kids a future without back pain | Turner Osler | TEDxStowe