Last time we looked, in brief, at one concept of modern biomechanics. This month I'd like to flit back a few years and look at one of the fundamental pillars of more traditional biomechanics. In particular I'd like to examine a word and concept that always makes me froth at the mouth and go purple (think the Incredible Hulk but less green). Overpronation.

For the sake of brevity I'll talk overpronation, but one could insert any of its more pretentious but basically synonymous cousins, hyperpronation, pathological pronation and excessive pronation (and any others you can think of).

As a biomechanics lead I have mentored many graduates and undergraduates in the ‘dark arts’ of biomechanics. Part of this process involves looking at assessment files. One of these generalisations seems to come up in almost every file I see! I also see it in referrals and frequently hear it from patients, especially those with access to Google. But does it belong in the ‘diagnosis’ box where I generally find it? What, when you get down to it, does overpronation MEAN?

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To examine overpronation we must first consider what constitutes pronation. Any fresh shiny graduate can tell you that pronation is a movement at the subtalar joint (STJ) comprising eversion, abduction and dorsiflexion. A more interesting question is why, if it causes so many problems, does pronation occur?

Two functions are generally offered for pronation: shock absorption and adaption to uneven ground surfaces - both vital things to protect joints further up in the chain. It is easy to forget in our righteous passion for supinating the foot that pronation is a natural and necessary movement which is an integral part of a healthy gait and function. I'll repeat that. Pronation is both normal and beneficial to the patient and its ABSENCE can increase the risk of pathology.

Some would have us believe that the proximal structures - knees, hips, pelvis etc - are only ‘aligned’ when the feet are in subtalar neutral, that they are ‘designed’ to work in that position and that if the foot pronates at all that they are ‘out of alignment’. Dear reader, this is not the case, and the seminal work by Root et al never suggested it was!¹ THAT belief has been born since. It is, perhaps, impolitic to speculate on who would stand to gain, financially, from propagating the belief among podiatrists and other health professionals that a situation seen in the vast majority of normal, healthy feet is pathological and in need of ‘correction’. And there I will stop with that line of speculation, as the smell of boiling tar is thick in the air and I see a few feathers waft past in the breeze. The truth, as agent Mulder astutely observes, is out there for those who seek it.

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