US PATENT 5,265,350 ON PRONATION


Here is what I said in my US patent (since expired) that I wrote in January 1991 and filed on February 3, 1991 about the existing philosophy in ski boots (aka – the prior art)

“The inventive technology disclosed by the present application, as will be described in more detail below, teaches the importance of accommodating and enhancing both bipedal and monopedal function by providing for freedom of medial movement of the inside ankle bone. This is in direct contrast with the prior art which teaches, in an indirect manner, that the ideal function for skiing will result from fixing the architecture of the foot in a position closely resembling that of bipedal function, thus preventing monopedal function. 

The prior art refers to the importance of a neutral sub-talar joint. The sub-talar joint is a joint with rotational capability which underlies and supports the ankle joint. The sub-talar joint is substantially “neutral” in bipedal function. That is to say that the foot is neither rolled inward or rolled outward.

If the foot can be substantially maintained in a neutral position with the arch supported and with a broad area of the inner aspect of the foot well padded, there will exist a good degree of comfort. Such a state of comfort exists because the foot is not able to roll inward (pronate) to a degree where significant mechanical forces can be set up which would allow it to bear against the inner surface of the boot shell. In effect, this means that initiation of the transition from a state of bipedal to a state of monopedal function, is prevented. This transition would normally be precipitated by an attempt to balance on one foot. If the foot is contained in a neutral position, traditional supportive footbeds (arch supports) are quite compatible with the mechanisms and philosophies of the prior art.

COMMENT: The objective of the conventional ski boot, whether intended or not, is to make skiing exceedingly difficult. Towards this end, the objective is comfort. A ski boot that renders the lower limbs dysfunctional can be very comfortable while at the same time making skiing exceptionally difficult. Although a priority, comfort in itself does not necessarily equate with good balance and control in skiing.

Problems arise when the foot is attempting a transition from a state of bipedal stance to monopedal stance. If the transition to monopedal stance or function can be completed without interference from the structures of the ski boot, all is fine and well. However, if the transition is allowed to proceed to a point where the mechanics associated with the monopedal function can establish significant horizontal forces, and the further movement of the foot is blocked before the transition can be completed, the skier will experience pain and discomfort at the points where the inner aspect of the foot bears against the structures of the footwear. This is the situation experienced by a majority of the skiers with prior art footwear. It is at this point where arch supports, if employed, also begin to cause discomfort. It should be noted that it is the normal tendency of the foot to pronate when weight bearing on one foot.

Footbeds (arch supports) may work in conventional boots (which traditionally do not allow natural biomechanics or movement of the foot to occur), but in a boot which accommodates and supports natural leg and foot articulation and function, arch supports can be detrimental.

When the foot attempts to pronate inside the ski boot, it is often the case that the ankle bone will come to bear against the inner surface of the boot shell. When contact of this nature occurs, pain and other related complications usually result. Since the consensus of those skilled in the art of ski boot design and modification is that pronation or the rolling inward of the foot is detrimental, and, thus, undesirable, provision is not made to allow for such movement. Rather, the structure of the footwear is intended to resist or even prevent it.

Thus, the problem with existing footwear arises due to the dynamic nature of the architecture of the foot. When the wearer is standing with the weight equally distributed between left and right feet so that the centre of mass of the wearer is manifesting itself in the centre between the feet, the architecture of the wearer’s foot assumes a specific configuration. As the wearer begins to shift his weight towards one foot so that the other foot bears proportionately less weight, the wearer’s centre of mass moves over the medial aspect of the weighted foot so as to assume a position of balance.

In order for this movement of the wearer’s centre of mass to occur, the architecture of the weighted foot must undergo a progressive re-alignment. Existing footwear does not adequately anticipate this re-alignment of the architecture of the foot and thus such footwear inhibits the wearer’s ability to assume a balanced position.”

While I am working on the video cited in my last post I will do a post next that describes how to assume a pronated position on one the foot and what it feels like.