This plane is largely about symmetry or a lack there of do to the hoofs response to uneven loading. If a horses leg came out the center of its body it might load the same on the inside as the outside and therefore grow as a perfectly conical hoof. This is obviously not the case. A horse with normal conformation will load the inside aspect of the hoof more than the outside because the inside is nearer the horses center of mass. In this situation the inner (medial) wall is subjected to more load and will be less conical and more vertical compared to the outer (lateral) wall which is taking less load.  The various conformational faults of base wide to base narrow and toe out to toe in will change which side is receiving more load, but that wall will always be less conical and more vertical (see ap image page). The side of the hoof that is loaded is that side which lands secondly. One side will hit the ground and then the weight of the horse will come down on the opposite side. This is an important and counter intuitive point.

Prior to picking up a horses hoof one should note how the hooves leave, land and load on level footing. The hoof should land evenly and therefore load evenly. However, some perfectly normal horses will land unevenly, a phenomena which has perplexed veterinarians and farriers for years. As a farrier I blindly applied sideways wedge pads to horses to make them land and load evenly, some improved and some became very sore. Currently, the only way I know to accurately sort through these situations is with the use of a true standing AP radiograph. The details of this method can be found in the paper “how to correct lateral medial imbalances.”

So lets break balance in this plane down to its most simple terms. Using the AP radiograph we will consider three values. The angle measurements from each wall and the P2/P3 joint tilt (distal interphalngeal or coffin joint).  The wall angles will tell us which side is being overloaded. The over loaded wall angle will be lesser of the two values or simply appear more vertical. The amount and direction of the P2/P3 joint tilt tells which wall is overloaded and if it is to the point of breakdown. Negative values are breaking down the outer wall and positive values the inner wall. Values of much above 3.5 degrees either way are on the verge of collapse. These hooves are truly out of level and in need of attention. The technique I have developed is detailed under the load shifting index.

The principle to this method is based on the age old technique of floating one side of the hoof, usually reserved for treatment of a quarter crack, a symptom of an overloaded wall. To apply this technique correctly the shoe is dropped down away from the hoof and no contact with the effected wall is made. Incorrect application would be trimming the wall away and putting a level shoe on. Conventional wisdom has been that taking the weight off of the wall was what begot the improvement. This may be true to some degree, however the shoe elevates the collapsed side of the hoof and shifts the load the opposite direction. The most handy shoe for this purpose is the ¾ bar shoe. Its application is clumsy in the hands of many farriers and it utilizes the frog for lift which is a sore spot for many horses in this situation due to inflammation of the coffin joint.

The other basic observation made in this plane is where the horses hoof breaks over. This is accomplished by simply observing shoe or hoof wear from the solar surface. Many horses break over to one side of midline. This has become increasingly more important as the use of square and blunt toe shoes have become more popular. Incorrectly applied these shoes can force a horse to break over midline who might prefer one side or the other.