Foot type. You know what we are talking about. The relation in anatomically and in space of the rear foot to the forefoot. We believe that this anatomical relationship holds key clinical insights to predictable biomechanics in that particular foot type.
Simply put, the rear foot can be either inverted, everted or neutral; Same with the forefoot. If the rear foot is inverted we call that a rearfoot varus. If the foot is inverted we call that a forefoot varus. If the rear foot is everted we call that a rear foot valgus and if the forefoot is inverted we call that a forefoot valgus.
Now think about the simple motions of pronation and supination. Pronation is dorsiflexion, eversion and abduction; supination is plantar flexion, inversion and adduction. If it remains in eversion, we say that it is in vslgus and that means they will be qualities of pronation occurring in that foot while it is on the ground. If the foot is inverted, it will have qualities of supination.
We think of pronation as making the foot into a mobile adapter and supination is making the foot into a rigid lever.
During a typical gait cycle the foot is moving from supination at initial contact/loading response to full pronation at mid stance and then into supination from mid stance to terminal stance/pre-swing. I know that if the foot remains and pronation past mid stance that it is a poor lever and if it remains in supination prior to mid stance it will be a poor shock absorbers. Foot type plays into this displaying or amplifying the characteristics of that particular foot type during the gait cycle: if this occurs at a time other than when it supposed to occur, then we can see predictable biomechanics such as too much pronation resulting in increased rear foot eversion, midfoot collapse, abduction of the forefoot and internal rotation of the knee with most often medial knee fall. Now, consider these mechanics along with any torsions or versions in the lower extremity that the patient may have.
This Wednesday night we will be discussing foot types and their biomechanics. Join us on onlinece .com for Biomechanics 314 6:00 MST
Dr Ivo Waerlop, one of The Gait Guys