Medial/Lateral changes in the bottom of the hoof

by David Farmilo
Accredited Master Farrier, Oakbank SA
PH 0418 835 186
www.horsefarrier.com.au


This is a study of the movement that I have observed which occurs during preparation of the hoof for either shod or unshod instances.

Many farriers/hoof carers get the blame for having got the levels wrong when trimming the hoof which then caused the horse to either paddle or dish. The possibility could be that he trimmed the hoof correctly but just put the shoes on too soon. Now if that sounds like a fairytale, then let me explain.

The desired aim in any preparation is to achieve a balanced symmetrical hoof and even heels. Viewed from the rear of the pastern there must be a T square across the heels and a level plane to the toe.

After trimming, and especially in cases where the hoof wall has been very distorted, the horse must be allowed a few minutes to weight bear on the hoof to allow it to settle into its new plane. Assuming you have already achieved the T-square in the back of the hoof, when it is re examined you may see it is no longer level or the ground bearing surface has moved. This is not a case of your eyes playing tricks with you. The larger and or heavier the horse the more movement there will be; some will actually move out of level three or four times before stabilizing.

To explain this movement which occurs in the bottom of the hoof more fully, we need to understand that the pedal bone (or p3 which is the bottom most bone of the horses leg) is attached to the hoof capsule by soft tissue or laminae, and behaves much the same way as the bubble in a builders spirit level - when the hoof capsule is allowed to grow or to wear unlevel for any length of time, the pedal bone actually moves over to get back under the leg bone above it to support the horse’s weight and its balance.

Very few horses have perfectly correct straight legs, and those that do will not develop any distorted re-growth between maintenance periods. For the majority, however, there is a continuing need to restore balance in the hoof. Whenever the cannon bone is offset on the knee joint, there will be a resulting flare in the bottom of the hoof. So often this flare causes the pastern to become turned in or out, as seen in foals. Corrected early enough the majority of deviated pasterns will straighten up, allowing the pedal bone to adopt a balance within the hoof capsule and stay there so long as the flares are corrected.

The prime objective must always be to achieve the T square at the heels so that they will land evenly; even if the horse is turned in or out both heels must land at exactly the same moment. We understand that in the foundered hoof the pedal bone has a tendency to rotate downwards at the tip, so we must also be aware that in the hoof which has a lateral/outside flare the pedal bone will move to the inside/medial to align itself within a position of balance under the upper leg, and with an inside/medial flare the pedal bone will move to the outside/lateral position within the hoof capsule.

Having corrected the flares and prepared the hoof within balance, leave 2 or 3 mm height in the hoof wall all around then allow the horse to bear weight for a few minutes. This will give the pedal bone time to settle into the corrected plane of the hoof capsule. Then re-inspect the lateral/medial balance and the T-square of the heels and re-correct any distortion which has occurred because of the pedal bone movement within the hoof capsule.

To reiterate, the greater the correction and the heavier the horse, the more movement will occur and the more delay should be given between dressing the hoof and fitting the shoe if we expect to achieve a correct leg action.