Sensible advice for aches, pains & injuries

10 Surprising Causes of Pain

Trying to understand pain when there is no obvious explanation

updated (first published 2007)
by Paul Ingraham, Vancouver, Canadabio
I am a science writer and a former Registered Massage Therapist with a decade of experience treating tough pain cases. I was the Assistant Editor of for several years. I’ve written hundreds of articles and several books, and I’m known for readable but heavily referenced analysis, with a touch of sass. I am a runner and ultimate player. • more about memore about

The world is full of unexplained pain. When I worked as a massage therapist, the most extraordinarily desperate people came to see me. Two memorable examples:

  1. A woman spends three days in the hospital with severe abdominal pain, but is cleared of every possible ominous medical cause … and then comes to see me?! A massage therapist!
  2. A man gets a ride in an ambulance with severe chest and left shoulder and arm pain, but doctors cannot find anything wrong with him … and then he comes to see me.

No pressure! And now I publish a busy website, and I get an email like this more often than I change my socks:

I’ve been to every medical specialist you can imagine. They can’t find anything wrong with me. The psychiatrist says it’s not in my head, and the rheumatologist says it’s not in my body. But something is causing my pain. It’s not an infection or a fracture or a cancer. It’s not a sprain or a pinched nerve or a little man with a knife. What else is there? What else is left?

What else indeed! When “obvious” and known causes of pain have been eliminated, what next? What else causes pain? How else can pain start, change, worsen? This article summarizes ten not-so-obvious ways to hurt: ten pain phenomena that might help you to understand pain that has defied diagnosis or explanation so far.

One of the principle qualities of pain is that it demands an explanation.

Plainwater, by Anne Carson

1. Muscle Knots

Muscle knots — myofascial “trigger points” — are a factor in most of the world’s aches and pains. Their biology is still mostly mysterious: conventional wisdom says they are tiny spasms, but they might also be a more pure neurological problem. Regardless, they can cause strong pain that often spreads in confusing patterns, and they grow like weeds around other painful problems and injuries, making them quite interesting and tricky. Although they are well known to many specialists and researchers, most doctors and therapists know little about them, so misdiagnosis is epidemic. See Trigger Points & Myofascial Pain Syndrome.

2. Sensitization

Pain itself often modifies the way the central nervous system works, so that a patient actually becomes more sensitive and gets more pain with less provocation. This is called “central sensitization.” (And there’s peripheral sensitization too.) Sensitized patients are not only more sensitive to things that should hurt, but also to ordinary touch and pressure as well. Their pain also “echoes,” fading more slowly than in other people. See Central Sensitization in Chronic Pain: Pain itself can change how pain works, resulting in more pain with less provocation.

Pain itself often modifies the way the central nervous system works.

3. Brain pain

This is another kind of sensitization: sometimes, the brain amplifies pain as a consequence of stress, anxiety, and fear. This is not “all in your head” pain, but “aggravated by your head” pain. Like an ulcer, there is a real physical problem — but it just happens to be unusually sensitive to your emotional state. Sometimes, the brain’s interpretation of a situation becomes a major part of the issue. Like picking at a scab, the brain can become excessively focussed on a pain problem. For more information, see Pain is Weird: Pain science reveals a volatile, misleading sensation that is often more than just a symptom, and sometimes worse than whatever started it.

4. Pathological sensitization

Yet another kind of sensitization: sensitization can also be caused by disease processes we do not yet understand. The first kind of sensitization is a more-or-less normal and common reaction to chronic pain. The second kind (“brain pain”) is powered by the worries of a frazzled brain. But there are also diseases that sensitize the nervous system: not a nerve pinch or lesion, but nerve failure. For instance, complex regional pain syndrome causes extreme pain, usually in a limb, and usually following some trivial tissue insult like an insect bite a minor cut. When it’s full-blown, the nastiness of this problem is impossible to understate — suicide is common — and yet there probably are milder variations of it. Many times in my career I have become quite convinced that a patient had to be suffering from some lesser form of CRPS, awful but not enough to clinch a CRPS diagnosis.

5. Muscle tension and contracture

Ordinary muscle tension itself can cause a surprising amount of pain. A leg or foot cramp is a common and extreme example, where no one has any doubt of the cause of pain. But imagine a muscle spasm much less strong, but lasting for days and days — or years! Although superficially a simple concept, there are actually several physiological mechanisms by which muscle can become shortened and painful for a long time, some well understood and straightforward (spasticity from neurological diseases), while others are quite mysterious (like spasms people are born with, as in torticollis or wry neck).

One particularly good and sinister example of muscle tension pain is the “MS hug”: a symptom of multiple sclerosis that feels like a painfully tight band around the chest, often experienced long before diagnosis. Although the feeling of constriction is the classic symptom, many patients also just experience widespread and erratic pain in the chest wall.

If your muscles are spasmed for long enough, they will actually “freeze” like that: essentially scarred into place, a phenomenon called “contracture.”12

6. Referred pain

Illustration of a dog barking up the wrong tree, representing the clinical problem with referred pain. The tree is labelled “where it hurts.” Behind the dog, pointing away, is another label: “the cause.”

Referred pain results in an amazing amount of medical barking up the wrong tree.

Anything that hurts inside the body — anything under the skin — is difficult for the body to locate. This is partly because we literally just don’t have enough nerve endings for it, and partly because the nervous system isn’t perfect and signals literally get “crossed.” The practical result of this is that internal pain with any cause may be felt somewhere completely different. Despite the fact that this phenomenon is well known, it still results in an amazing amount of medical barking up the wrong tree. Referred pain isn’t exactly a “cause” of pain, but it belongs in this list because it’s an important concept that can help to explain many pain problems that otherwise don’t make sense. For instance, both of the examples at the beginning of this article were cases where referred pain fooled doctors — in both cases, the pain was caused by a trigger point in a nearby muscle, not by vital organs. The doctors simply looked in the wrong place!

7. The pain of stuckness

Here’s a simple experiment: assume an distinctly awkward posture, and within minutes you will probably experience severe pain. Why? You haven’t ripped or torn anything. But we are wired to avoid this situation, because every cell in our body depends on nearly constant movement to survive. And so the nervous system takes it very seriously whenever tissues feels “stuck.” The exact mechanism of pain is probably nerve endings that detect tension on cartilage, ligaments and tendons. Continuous tension on these structures may be interpreted by the nervous system as a serious threat. But here’s the kicker: you can induce this reaction quickly with an obviously awkward posture … or you could do it slowly and insidiously with surprisingly subtle poor posture, muscle imbalances, joint dysfunctions, or anything that deprives tissue of full movement. When a joint feels “stuck,” for instance, and there is no obvious way (and sometimes no anatomical way) of moving to get “unstuck,” the sensation can escalate to a screaming itch-you-can’t-scratch. This is may be the main causes of neck cricks, for instance, and scads of other miscellaneous aches and pains. Unfortunately, postural correction is a challenging and sketchy business.

Actonel (risedronate) is one of the more popular bisphosphonate drugs, any of which may cause severe musculoskeletal pain years after first exposure.

Actonel (risedronate) is one of the more popular bisphosphonate drugs, any of which may cause severe musculoskeletal pain years after first exposure.

8. Drug side effects, especially bisphosphonates and statins

On January 7, 2008, the U.S. Food and Drug Administration alerted health care professionals and consumers to the unusual severe side effects of a popular class of drugs for osteoporosis and Paget’s disease, the bisphosphonate (Wikipedia). They can cause “severe and sometimes incapacitating bone, joint, and/or muscle pain” which “may occur within days, months, or years” after first taking the medication. This medication has almost certainly explained some otherwise inexplicable pain in some of my patients over the years! Alendronate and risedronate are the two most popular bisphosphonates, and they are usually prescribed for osteoporosis or for a bone-deforming condition called Paget’s disease. If you are 40+ and grappling with a mysterious pain problem, check your medicine cabinet for bisphosphonates in particular, but of course any other medication that could cause pain as a side effect.

And then there’s the statins, like Lipitor and Crestor: the drugs that lower our blood cholesterol can also cause pain. Statins are important and widely used drugs, and their deleterious effect on muscle is so common that is a diagnosable condition: statin myalgia.3 There is some controversy about how prevalent it really is,4 but a few patients, about 1 in 10,000, get a more obvious, serious case of muscle poisoning, rhabdomyolysis,5 and an even rarer and more serious condition afflicts 1 in 100,000: statin-associated autoimmune myopathy.67 There is good news, though! Ridding yourself of these side effects, even the worst, is usually as easy as lowering the dose or switching to another statin.

9. Analgesic rebound

This almost counts as a drug side-effect, but it’s an important enough phenomenon in its own right that it deserves separate description. When you take a lot of analgesics — pain-killers — it’s possible to pre-empt the production of your body’s own pain-fighting molecules. Endorphin production, for instance, will drop. This can have disastrous consequences when you stop taking the drugs, resulting in worse pain than ever. This is part of the phenomenon of the well-known serious withdrawal symptoms from some drugs; it is a less well-known problem with over-the-counter pain-killers. Although this phenomenon isn’t particularly mysterious or difficult to identify, it does show us something important about how pain works: we aren’t entirely without our own defenses, and those defenses can actually be undermined by artificial help. And there are scenarios where analgesic rebound may be difficult to detect. Given how extremely common analgesic usage is, it’s likely that people with recurrent headaches may suffering primarily from bouts of rebound pain, occurring in the occasional gaps between erratic but generally intensive self-prescribing of pain killers.

I have a good story about a terrible withdrawal-induced headache: see my headache tutorial.

10. Stupid, stupid neutrophils

Neutrophils are defender cells that are supposed to destroy bacteria that invade wounds, a normal part of the inflammatory response to injury. Bizarrely, neutrophils go to work even when the wound is sterile, not open to the outside world. Like an overzealous police force with nothing better to do, they also attack a common cellular organ, mitochondria, whenever it is spilled from cells by injury. Mitochondria are actually honoured symbiotic guests that convert our food to energy for us. Normally we live out our lives in perfect harmony with mitochondria, biological BFFs. But when they get the chance, neutrophils target and hunt them like they are invaders8 because for millions of years they haven’t gotten the evolutionary memo that mitochondria should be left in peace.

Inflammation is excessive for this reason: every trauma causes pain that is too loud for too long, because a significant portion of the inflammation is due to this SNAFU immune system policy of attacking mitochondria. There are many perverse sources of pain in pathology, but this one really stands out as being particularly ridiculous and unfair. It does have one practical implication: it directlys suggests that it’s quite reasonable to try to control and limit inflammation with things like Voltaren® and icing. Contrary to the popular notion that inflammation is “natural” and therefore good, inflammation is definitely exaggerated, and could do with some controlling!

For more information, see 10 Surprising Causes of Pain: Trying to understand pain when there is no obvious explanation.

This is a clear glitch in biology: they attack because they mistakenly interpret

And of course all of these phenomena can and regularly do get mixed up together in unholy combinations, most of them having the capacity to cause or complicate any of the others. It keeps my job interesting.

About Paul Ingraham

Headshot of Paul Ingraham, short hair, neat beard, suit jacket.

I am a science writer, former massage therapist, and I was the assistant editor at for several years. I have had my share of injuries and pain challenges as a runner and ultimate player. My wife and I live in downtown Vancouver, Canada. See my full bio and qualifications, or my blog, Writerly. You might run into me on Facebook or Twitter.

Appendix: So what happened with those two pain cases?

At the beginning of the article, I described two cases of severe undiagnosed pain:

A woman spends three days in the hospital with severe abdominal pain, but is cleared of every possible ominous medical cause … and then comes to see me?! A massage therapist!

A man gets a ride in an ambulance with severe chest and left shoulder and arm pain, but doctors cannot find anything wrong with him … and then he comes to see me.

I got lucky with both of these cases, and I was able to treat both of them quickly and easily. There are many ways to hurt, and success was hardly guaranteed. I saw many patients with strange pains I was never able to diagnose. But both of these cases involved surprisingly clear and and treatable trigger points: hypersensitive spots in muscle tissue, causing more pain than anyone thought possible.

In the woman’s case, the trigger point was in her iliopsoas muscle, a muscle deep in the abdomen and extending downward through the pelvic that is the subject of much hype and legitimate skepticism. However, it is possible to massage it in some patients. There’s very little to tell: I guessed that it might be the problem, found the trigger point, gently massaged it for a few minutes… and that was the end of her misery. Just like that!

The man’s case was even more straightforward: he had a trigger point in his pectoralis major muscle. It was easy to find, as the muscle twitched violently when I palpated it, the most robust example of a “jump sign” I ever saw. It was nasty, but in twenty minutes of massage we reduced the “heart attack” pain by 80%. The next day it was gone, and it stayed gone for as long as I knew him — years after that. I tell his story in more detail in my trigger points book.

Related Reading

What’s new in this article?

Added sidebar about the basic types of pain, nociceptive and neurpathic. Added #10, about exaggerated inflammation.


  1. Csapo R, Maganaris CN, Seynnes OR, Narici MV. On muscle, tendon and high heels. J Exp Biol. 2010 Aug;213(Pt 15):2582–8. PubMed #20639419. PainSci #55265. Chronic heel wearers do have shortened calf muscles, stiffer Achilles tendons, and a smaller ankle range of motion. BACK TO TEXT
  2. Chen CK, Yeh L, Chang WN, Pan HB, Yang CF. MRI diagnosis of contracture of the gluteus maximus muscle. American Journal of Roentgenology. 2006;187(2):W169–74. PubMed #16861506. PainSci #55849.

    From the abstract: “Gluteal contracture manifests characteristic features on MRI, including an intramuscular fibrotic cord extending to the thickened distal tendon with atrophy of the gluteus maximus muscle and posteromedial displacement of the iliotibial tract.”

  3. Di Stasi SL, Macleod TD, Winters JD, Binder-Macleod SA. Effects of Statins on Skeletal Muscle: A Perspective for Physical Therapists. Phys Ther. 2010 Aug. PubMed #20688875. BACK TO TEXT
  4. Ganga HV, Slim HB, Thompson PD. A systematic review of statin-induced muscle problems in clinical trials. Am Heart J. 2014 Jul;168(1):6–15. PubMed #24952854.

    In this review of several statin trials, only slightly more patients had pain on statins than without (placebo): just 12.7%, compared to 12.4%. You could conclude from this data that there actually is no such thing as statin mylagia! But it probably probably is a real phenomenon, which is highly plausible based on the existence of rarer but very severe side effects on muscle (see Mammen or Statin Therapy). We don’t have very good data about it, it’s mostly not severe, and it’s hard to distinguish from the “background noise” of many other common causes of musculoskeletal pain.

  5. “Rhabdo” is a nasty but also very interesting condition. I discuss it in detail in Poisoned by Massage. BACK TO TEXT
  6. Mammen AL. Statin-Associated Autoimmune Myopathy. N Engl J Med. 2016 Feb;374(7):664–9. PubMed #26886523. BACK TO TEXT
  7. Regarding classification, professionals should take a look at a great 2004 interview with Eliot A. Brinton, MD: “There are 4 interrelated terms for muscle problems that can occur with statins. Unfortunately, they are often confused even by healthcare professionals ….” (Technical note: this document is freely available, but direct linking will hit a paywall. Medscape only reveals the whole thing to people arriving from a Google search. Simply search for do a Google search for it to get around the paywall.) BACK TO TEXT
  8. McDonald B, Pittman K, Menezes GB, et al. Intravascular danger signals guide neutrophils to sites of sterile inflammation. Science. 2010 Oct;330mcd(6002):362–6. PubMed #20947763. BACK TO TEXT