“Spasm,” as in a “back spasm,” is an informal, non-specific term often used to “explain” musculoskeletal pain.
Musculoskeletal pain — especially back pain — is carelessly attributed to “spasms” by practically everyone … but it does not refer to any specific clinical entity like dystonia, spasticity, or cramp. So what is it? Is there such a thing as a “spasm”? It’s amazingly hard to know.
Three major assumptions about “spasm” are often blended:
- spasms hurt — they are a major mechanism of pain, especially in the back and neck
- spasm is often “protective” — muscle guarding or splinting
- painful spasms cause themselves — a pain-spasm-pain vicious cycle
All of these ideas are repeated ad nauseum by both clinicians and amateurs. Among the academics and experts, there’s a long, erratic history of debate over almost zero data, fighting over scraps. No one actually knows if they are true, and there’s a good chance they are not.
For many years I denounced them as myths, or misleading half truths at best. My contrarianism was overconfident, and based mainly on my deep distrust of vague claims. They smell like myths … but I can’t actually refute them with good evidence, because there is no such evidence. At best I can point to some red flags. Here are some basic concerns:
- Cramps are obviously painful, but so the visible contraction of the muscle and its effect on joints is also obvious. If back and neck pain are caused by contracting muscle, why can’t we see and feel it contracting? And why aren’t we actively fighting to keep the muscle elongated, as we must with cramps?
- If pain and spasm cause each other, why wouldn’t the vicious cycle escalate at least to the point of being an obviously contractile phenomenon, like a cramp? It seems like it must either be so limited that it’s not very “vicious,” or it simply doesn’t happen.
- “Protective” muscle spasm clearly does not make biological sense with many injuries. For instance, it would be dangerous to contract muscles around a fracture: that would tear it apart!
Although those warning signs exist, there are also clinical clues that there are kernels of truth to these ideas about “spasm,” and it’s generally unwise to underestimate the complexity of muscle physiology and motor neurology. As with so much else in medicine, the truth is simply unknown.
These ideas are now covered in more detail on PainScience.com after a series of updates. See: