Mechanical vs Non-Mechanical Pain

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

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.

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:
   • Red Flags for Low Back Pain
   • Masqueraders of Spinal Pain
   • Alan Taylor – Aortic Aneurysms. Thanks Alan for the heads up on twitter!
   • IFOMPT Framework for Examination of the Cervical Region
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.

Thanks for reading.