Basic Mechanics of the Hoof and Horseshoe - Continued

Rolling & Sliding

by
James Rooney, D.V.M.

It is the basic premise of this essay that the sensitive and insensitive laminae and the horn tubules of the hoof wall are constructed in parallel with the primary force exerted on the foot since the laminae and tubules are best able to sustain the applied force in that configuration, Fig.1 (After Ellenberger and Baum 1927).

Figure 1

This is true whether the horse is standing still or at any gait and velocity when moving. Fig. 2 makes the mechanical case although for many readers it may be sufficient to simply state that the vertical force on the foot combines with the tensile force exerted by the deep flexor tendon to assure – normally – that this parallelism of force and laminae is maintained. For those who wish more please read on.

Figure 2

To the left in Fig. 2 are shown the vector forces on the foot when the horse is standing still or the foot has impacted with and is fully in contact with the ground. R is the actual, resultant force in the foot and is composed of the vertical force, F and the horizontal force, H..

As the vertical force increases from impact to midsupport the F force increases to a maximum as indicated in the figure to the right. At the same time the fetlock is dorsiflexing, increasing the tension in the deep flexor tendon, indicated by the longer horizontal (blue) vector in the right figure. Normally, the increase of F and H are in phase with each other, so that R, while becoming larger, does not change direction. Therefore, R, the force in the foot, remains in parallel with the laminae of the hoof wall.

There are some subtleties involving the change of direction of the deep flexor tendon and its components, but these do not change the argument presented.

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