What are corns?

Corns are bruises of the sole which occur at the angle of the sole between the hoof wall and the bars, i.e. at the 'seat of corn' Corns most commonly affect the medial (inside) aspect of the front feet. They are an important cause of lameness in shod horses.

Bruises are traumatic injuries which result in haemorrhage into the sensitive tissues of the sole. Haemorrhage increases pressure in the sensitive tissues which results in pain. Haemorrhage causes discoloration in the typical manner of a bruise occurring anywhere else. Corns may develop acutely (suddenly) or chronically (over time). Chronic corns tend to occur in horses with low heels where the walls collapse inwards persistently traumatising (injuring) the seat of corn.

Corns may be classified as:-

• Dry corns - haemorrhage between the sole and sensitive tissues (see bruised sole) causes thinning of the sole over the seat of corn. Paring with a hoof knife may reveal a red bruise, although this may be difficult to find until the affected horn grows down towards the ground level.

• Moist corns - trauma causes inflammatory fluids to accumulate under the sole giving the impression that the horn of the sole is wet.

• Suppurating corns - penetration has occurred and infection has developed underneath the sole at the seat of corn resulting in pus formation (see our hand-out on pus in the foot).

What causes corns?

Corns are almost invariably caused by shoes which fit improperly so that they are fitted short and tight at the heels, traumatising (injuring) the seat of corn. In some cases, shoes have been left on too long so that as the foot grows the shoe is carried forward causing the heel branches to traumatise the seat of corn. In other cases, stones may become lodged between the shoe and the seat of corn, resulting in injury and bruising. Excessive weight bearing at the heels, as in a horse with low heels or where heel calks or studs have been used, may traumatise the seat of corn.

How are corns diagnosed?

Corns cause a horse to show signs of lameness, the severity of which depends upon the degree of bruising. The lameness is characterised by a shortened anterior stride phase with toes contacting the ground, saving the heels. Lameness is usually most evident on hard ground and when the horse is circling. If corns affect both front feet, a bilateral foreleg lameness may not be noticed until the horse is lunged or ridden in small circles.

There is usually a pain response to the application of hoof testers specifically over the seat of corn. The horse’s digital pulse strength may be increased and the feet may appear warm to the touch.

A dry, moist or suppurating bruise can be seen at the seat of corn when the overlying sole is pared away.

Radiographs may be used to rule out other causes of lameness in the heel area such as sidebones, navicular disease or pedal osteitis.

How are corns treated?

The horse’s shoes should be removed as a first step. Dry and moist corns are pared with a hoof knife to relieve pressure, suppurating corns are opened to drain and treated as for 'pus in the foot'. Be careful not to pare the sole excessively in thin soled horses or the condition may be worsened. A poultice, followed by dry protective bandaging, may help to speed recovery and the horse should be rested until recovered.

After rest and recuperation, the horse can be re-shod ensuring that the shoes are fitted long and full at the heels to support the heels and encourage heel growth.

How can corns be prevented?

Regular hoof trimming and good farriery is the best way of preventing corns in horses. It is wise to avoid excessive foot trauma on hard going.