Ankles and Anthropology – an exercise in procrastination.

 

In my role as Health Professional I have undertaken a certain amount of research, both at undergraduate level  and as a part-time post-graduate student.

In 2002 I was awarded a research MSc (for the rather snappily-titled Foot function and normal Coronal plane range-of-motion at the ankle-joint-complex thesis) by Durham University. My professors were very indulgent and allowed me several extensions over a seven-year period. Some of the delay (a part-time MSc usually takes three years) was due to a close family bereavement. The rest of the tardiness was squarely my own fault. Switching from PhD to MSc didn’t help, but neither did my becoming totally engrossed in the subject, rather than shooting for degree completion. As an aside, I met someone who took fourteen years to complete his PhD at Imperial College, London – unknown to me at the time, the delay in completing my MSc was not entirely unprecedented.

Why research ankle movement? Well, when I did my research we had some range-of motion figures which everyone assumed were correct, even though they differed quite markedly depending on who you read. Rather surprisingly, at the time of writing this is still the case. Recently, I was invited to submit a Paper on this subject to a UK Podiatry magazine. My work has never been written up and published before, so I was delighted, after a sixteen-year academic rest, to re-visit the thesis in December 2017,  resurrect the data, and re-examine the conclusions.

On the re-visit I realised I had missed the most important finding in my original thesis. That not only do we probably have much more movement in our ankles than previously reported in the literature, but that when ankle movement is induced by a small, measured force (in this case, 3.9 Nm) it is relatively unrestricted by ligaments, tendons, other structures in the ankle, and bony geometry (the way the bones fit with each other) until around 64 degrees from horizontal of inversion – that’s the foot rolling in on the ankle – is reached. What this means in plain language is that your ankle ligaments will not stop you going over on your ankle – they are incapable of doing so – until your ankle is bent right over at 60 degrees or so. How much is that? take a look at the protractor in the heading photograph – I set that at 60 degrees.

This is not some kind of design fault. It is more likely to be a survival trait which  allows Homo Sapiens to comfortably stand erect, walk, and run on a variety of surfaces. The more flexibility the ankle has in inversion, the better able it is to conform to rough terrain. This means that muscular power, not fixed ligamentous or tendinous structures,  controls gradual attenuation of ankle flexibility as the foot moves into a foot-flat position. Apply the same force in the other direction, and the ankle becomes a very stable structure, due mostly to fixed ligamentous, tendinous, soft tissue structures, and bony geometry, around foot flat, or horizontal – this, unsurprisingly, is a mechanically advantageous position for normal walking and running.

The importance of this finding is that the major joints of the foot and ankle have probably not adapted for life on the hard, flat surfaces which we in the West spend most of our time on. Probably more importantly is that the research offers an explanation of how the ankle joints of Homo Sapiens operate so effectively. Whatever the ground surface – soft, hard, undulating or flat – our feet, if healthy, will conform to it, and in turn will allow us to conform to it quite happily, with or without footwear.

The finding is likely to be of interest to Anthropology. As I write this, and with the benefit of 16 years of hindsight after completing my research, I cannot conceive of a better design for a low energy demand, lower limb/ground interface which allows for bi-pedal balance, support and slow/rapid ambulation over a variety of surfaces and distances.

Please note that the first part of this research has now been published.

 

 

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