What causes corns?

Q: I do a lot of road riding and 10 to 20km forest rides, and my horse has developed corns on his heel. Can you tell me what corns are (are they anything like the corns that humans get) and how can they be treated? Is it caused at all by the surfaces he is worked on?

Ricky, Auckland

A: Corns are a bruising which is occurs in a particular place in the hoof called appropriately, “the seat of corn”.

The seat of corn can be seen on the solar surface on the inner area of the hoof wall turns to form the bars. There’s two on each hoof – one on the inside and one on the outside.

The causes of corns have some similarity to other types of bruising. That is, they can be caused by hard impact, regular concussion to the area and sometimes disease/injury.

The pressure from an ill-fitting or shoe that has been left on too long (with the hoof growing over the shoe) is a classic cause of a corn. The shoe presses on the seat of corn and causes a corn to form. Working the horse regularly on certain (usually harder) surfaces can be a contributing factor. The co-lateral cartilages of the pedal bone are directly over the seat of corn and more often than not play an important role in helping corns to form. Sometimes these cartilages can be the cause of a corn when bony changes occur within the hoof capsule. A veterinary diagnosis may help establish the likelihood of this and it’s most certainly something worth investigating when the initial farrier alterations have been tried and the problem doesn’t improve or there’s a persistent recurrence.

It’s also worth checking to see if dirt or debris is getting lodged under the shoe and pressing on the seat of corn – this could be quite simple to eliminate if it’s the case.

A minor corn is often seen as reddening on the solar surface of the foot and can be eased away by the farrier or vet to remove the pressure on the area.

More severe corns will continue deeper into the hoof (often in a relatively tubular shape towards the inside) and can sometimes be wet and bloody and turn necrotic.

As with any bruise, we expect to see some degree of lameness in a horse with a corn.

Treatment involves identifying the cause of the corn and removing that cause. Often carefully cutting the corn away and attempting to prevent recurrence by adjusting the shoeing or hoof balance will be enough. For deep seated corns, some further veterinary treatment may be necessary which allows the seat of corn to drain and then protect any damage to sensitive structures.

In answer to your question, yes, the surface you’re working on could be a contributing factor to the problem. Talk things through with you farrier and vet if necessary and together you can hopefully find a solution that works for your horse.

David Hankin Dip.WCF

first published in NZ Horse & Pony magazine December 2011

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