By Vicky Rowlands BVM&S CertEP MRCVS, Ashbrook Equine Hospital.
Hoof conformation is one of the most important factors in allowing a horse to live an athletic life free from lameness. The adage ‘no foot, no horse’ is as true today as when it was first phrased.
Hoof conformation is a result of the horse’s genetics, conformation, job and the regularity and quality of farriery they are given. Maintaining a healthy, balanced hoof shape can dramatically reduce the risk of lameness arising from the lower limb or hoof. Without regular appropriate farriery input, even a normal shaped hoof can easily become unbalanced and put undue stress across the hoof capsule making it likely to crack or the horse to become lame.
When assessing hoof balance, we look for at foot conformation standing still (static) from the front, side and when the limb is lifted. Foot balance is also assessed when the horse is walking (dynamic). It is important that the foot is symmetrical both when looking at it from the front and also symmetrical around the midline of the frog when the foot is lifted. When viewed from the side, the hoof pastern axis should be a straight line running through the pastern, the coronet band and the hoof capsule. The hoof pastern axis can be described as straight, broken forwards or broken backwards. The ideal axis will always be straight as any deviation from this will result in abnormal loading or pressure across the foot and the soft tissues of the lower limb.
When viewing the horse walking towards you, the horse’s foot should land with the inside and outside of the foot striking the ground simultaneously. When viewed from the side, the toe and the heel should land simultaneously. This is most easily assessed either by the farrier at routine trimming or shoeing or at a veterinary assessment for lameness or poor performance.
Horses commonly show medio-lateral imbalance whereby one side of the foot is longer than the other and the hoof will strike the floor unevenly. This results in excessive pressure across the lower limb joints, especially the coffin joint and it’s collateral ligaments. When viewed from the side, if the toe lands first, it can suggest pain in the back or caudal part of the foot and if the heel lands first, it can suggest toe pain or pain associated with laminitis.
If any foot imbalance is noted at static or dynamic examination, radiographs can help identify the extent of the problem and help the farrier to trim and shoe the foot appropriately. If the limb is straight and the problem is solely due to the foot then this can usually be corrected over 3-5 shoeings. If an adult horse has a limb deviation, like toe in or toe out, which contributes to the hoof imbalance, then the limb can never be straightened. It is still vital to maintain the best foot balance possible in these horses in order to minimise abnormal forces across the lower limb joints and reduce risk of lameness originating in these joints. Limb deviations in very young foals should always be addressed, with the aim of producing adult horses with straight limbs and less risk of foot imbalance and future lameness problems.
If there is medio-lateral imbalance, the farrier will trim the inside and outside walls of the hoof to different levels in an attempt to make the foot land equally on the inside and outside walls. In more extreme cases, if the horse is shod, the shoe can also be thinned on one side to help the foot land flat.
In the case of feet which land toe or heel first, lateral radiographs taken from the side of the horse, can help identify the true hoof-pastern axis, any underlying laminitis or reverse rotation of the pedal bone. In the case of very flat feet, collapsed heels or reverse rotation of the pedal bone, the farrier will sometimes use wedges under the heels of the shoe to improve the hoof-pastern axis. These will usually be used for a few shoeings but are not often used long term as they can occasionally cause heel problems with continual use.