By September 20, 2015 3 Comments Read More →

Mechanical vs Non-Mechanical Pain

I wrote a while back about posting in relation to the “Inverted Pyramid”.

invertedpyramid1

The inverted pyramid principle is aimed at keeping what we do simple. I think as a profession we have a tendency to overcomplicate many things and “fluff” around doing and focusing on things that in some cases are of very little importance. Instead we should focus on the important stuff. Although maybe my brain just can’t handle the complicated things!

The first topic in this series will be how to classify pain. I have covered pain types previously in the following posts:

  1. Pain Classification
  2. Classification of Central Sensitisation, Nociceptive Pain and Peripheral Neuropathic Pain
  3. Classification of Radiculopathy and Peripheral Neuropathic Pain
  4. Types of Pain
  5. Central Sensitisation

Now I will be the first to admit that the above posts can get confusing. I get confused reading over them again now! I don’t think that it helps that when I read the scientific literature on pain I see the following terms to describe pain types pop up routinely:

  • Nociceptive pain
  • Peripheral Neuropathic pain
  • Central Neuropathic pain
  • Inflammatory pain
  • Systemic Inflammatory pain
  • Nociceptive Inflammatory pain
  • Central sensitisation
  • Peripheral sensitisation
  • Functional pain
  • Dysfunctional pain
  • Neuropathic sensitisation
  • Central Hyper-excitability
  • Neurogenic pain
  • Pathological pain

My head hurts from all of the pain types!

I also wonder if clinicians are sometimes arguing about what “pain type” the patient has but are in essence describing the same symptoms and agreeing on the same treatment needed. So to avoid focusing on the “fluff” and arguing about which of the myriad of pain types someone might have, perhaps we should simply initially focus on how the pain “behaves”.

In my clinical experience I feel that the best start point when initially assessing pain is to simply view it as either “Mechanical” or “Non-Mechanical”. Patients might also have a mixed behaviour of mechanical and non-mechanical pain. I first encountered this terminology when I began reading, and applying, the “O’Sullivan Classification System”. This brief section from a chart in Vibe Fersum et al (2013) (a free article by the way) summarises these two terms very simply, but effectively.

Blog_MvsNM

Whilst I realise the Vibe Fersum article is in relation to axial low back pain, there is no reason why you cannot apply this approach to any other area of the body. For example, does my knee patient have localised knee pain that worsens with certain movements and settles with others (mechanical pain) or do they have “knee pain” that encompasses their entire leg and is constantly painful, with pain that triggers to a 10/10 severity when someone brushes their leg, and takes 3 days to settle down (non-mechanical pain).

Granted the above are brief examples, but I hope it makes sense.

Using the above chart and thought process is a nice start point to begin the process of differentiating between mechanical and non-mechanical patterned pain. It can then help direct us to what treatment to apply/recommend. This will be a future post.

A couple of key points to finish:

  1. Don’t forget that non-mechanical pain and mechanical pain can also be due to Red Flags. It is important to screen for these potential issues. In this age of the “Biopsychosocial approach” (I thinks its great by the way) we need to be be mindful that “Biomedical” issues can still occur, and need medical review if they are present. Screening for Red Flags is quick and easy. Don’t miss them. See some of the following posts/blogs for more information:
  2. Remember also that mechanical pain might also be something that needs investigating, for example a tendon rupture in a young patient. Don’t forget about potential “structural” problems that can occur in patients.

So overall I think classifying your patients as having mechanical or non-mechanical patterned pain, or a mixture of both, is a nice starting point in clinical practice because it keeps it simple for us and the patients.

kiss05

Thanks for reading.

Posted in: Clinical Reasoning, Pain

About the Author:

Mark is a Specialist Musculoskeletal Physiotherapist who consults at both Insight Physiotherapy and Pain Options, in Perth, Western Australia. He specialises in the assessment and management of persistent/chronic musculoskeletal pain. In addition to his clinical role he maintains regular involvement in education of the profession having held a Teaching Fellow position at the University of Western Australia for 10 years and regularly presenting at courses and seminars through the Australian Physiotherapy Association and private education sector. Mark is also a Facilitator for the Australian College of Physiotherapists Specialisation Training Program and a Branch Councillor on the Western Australian Branch of the Australian Physiotherapy Association.

3 Comments on "Mechanical vs Non-Mechanical Pain"

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  1. Cam says:

    Hi Mark,

    I also think us physios (and scientists in particular) have a tendency to overcomplicate things and get way off track.

    But I don’t think we can necessarily use pain-on/pain-off with movement to make the distinction between mechanical/nociceptive and ‘other’ pain. For example, if someone has learned “never bend your back – it’s very bad for you”, then doing so could trigger pain in the absence of any mechanical deformation. Every single time they bend past their knees, a memory circuit is triggered, thresholds are lowered, and BAM…. pain.

    Knowing what we do about pain, I reckon it’s safe to assume most pains have much more to do with the brain than the mechanics in the periphery. So I treat brain/CNS processes almost exclusively. Also, we have virtually no effective treatments for assisting tissue healing or inflammation, so there’s no point wasting time on the periphery. Peripheral treatments do act as a good foil, however.

    Regards,

    Cam

    • Mark Gibson says:

      Hi Cam,

      Great points and I completely agree, after all we can’t have a patient without them having a brain/CNS, although I do wonder about this sometimes with some of my patients….:)

      Secondary to this I reckon that we are pretty much treating the brain/CNS with the vast majority, if not all, of our treatments.

      I do however think as a start point that differentiating mechanical vs non-mechanical can at least allow us to start to theorise what direction of treatment might be needed i.e. a patient with significant widespread pain with dominant non-mechanical symptoms is probably more likely to need a wider spectrum of multidisciplinary consideration for treatment and more intensive “neuroscience” “explain pain” type treatment. Someone with dominant mechanical symptoms less likely to need to above. As you have nicely outlined the above however is not “set in stone” and there are always outliers. Your example of the back pain patient being a classic example. I recall seeing a “mechanical” back pain patient recently who stated even thinking about bending their back triggered pain. Clearly no mechanical deformation but generally mechanical symptoms reported and demonstrated in the history and physical examination.

      Thanks again.

      Cheers
      Mark

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