WHEN you lift a horse’s foot to examine it, the majority of the surface you’re looking at is the sole. A normal sole is slightly concave, so if you picture an unshod horse standing on a concrete yard only the hoof wall and heels are actually contacting the ground. The hoof wall is made of keratin, which is a very tough protein, so it’s well adapted to carry the majority of the horse’s weight.

The sole is also made of keratin, but it’s not quite as thick and resilient as the wall. The entire hoof is slightly flexible, so during movement (especially at higher speeds) the foot will compress during weight bearing, allowing the frog to come in contact the ground. There’s a network of veins under the sole and this ground impact helps squeeze the blood out of these vessels and back up the horse’s limb, against the force of gravity. In this manner, the shape of the sole and frog contributes to circulation of the blood, as well as grip and shock absorption when moving.

The sole overlies a dense network of tiny blood vessels, which nourish the laminae – the Velcro-like fingers of interlocking tissues that tightly bind the sole and hoof to the pedal bone.

Trauma to the sole, e.g. stepping heavily on a sharp stone, can result in damage to these vessels. A pocket of inflammation or bleeding may develop between the sole and the pedal bone: a ‘stone bruise’. This type of injury is very common and many horses will develop a bruised foot at some point in their lives.

Reddened or bruised

Once a stone bruise occurs, the horse will feel sore. The hoof wall cannot stretch and so the pressure within it rises due to swelling, further compressing the painful tissues. The horse will generally bear some weight on the limb, but will be lame at the walk or trot and may flinch if pressure is applied over the affected area. The pulse in the arteries supplying the foot will typically be increased or ‘bounding’. Occasionally, a reddened or bruised area may be visible on the sole, especially if the horse has pale hooves.

The horse’s conformation is also a risk factor for sole bruises. Flat-footed and thin-soled individuals are more susceptible, as are those with a long-toe, low-heel conformation, due to the relative lack of cushion between the ground and the sensitive interior of the foot. Regular foot care and trimming helps to minimise the risk.

Most solar bruises will heal uneventfully. Treatment typically consists of box rest and anti-inflammatory medication to reduce the pain and swelling. Removing the shoe and wrapping the foot may help. Cold-hosing, poulticing or icing the foot can provide additional relief. Consult with your vet and farrier as appropriate and avoid putting the horse back into work until the swelling and lameness has resolved – this typically takes about three to 10 days, depending on the severity of the bruise.

Pocket of infection

Occasionally, a solar bruise can get infected and become a solar ulcer or abscess. Any pocket of blood and inflamed tissue is a suitable environment for bacterial growth, so if the sole was pierced at the site of injury a pocket of infection can arise under it (Figure 1). Granulation tissue or ‘proud flesh’ may also develop, especially if healing is delayed by a complication such as the presence of grit or dirt. These subsolar ulcers or infections are less common than an uncomplicated bruise, but the horse tends to be in noticeably more pain. If any horse becomes reluctant to put their foot flat on the ground, especially within 48-72 hours of a foot injury, don’t wait to see if it gets better by itself.

Other things to look out for are swelling of the lower limb, heat in the foot and very strong or ‘bounding’ digital pulses in the affected leg. The vet or farrier can open the abscess on the sole to allow it to drain (see Figure 2).

This should give the horse immediate relief. Pain relief is always recommended in these cases and antibiotic therapy or surgical intervention may be indicated, if there’s a concern that the infection involves the coffin joint or navicular bone. The horse’s vaccination history will also need to be checked to make sure they are protected against tetanus. The horse’s foot will need to be kept meticulously clean and dry until the defect in the sole has healed.

As with all things horse-related, prevention is better than cure. Daily hoof cleaning ensures stones or other items lodged in the foot are noticed and removed. Regular exercise promotes good circulation and helps keep the horse from carrying excessive weight. Pay attention to the surface when working your horse, try to avoid stony or uneven underfoot conditions. Inspect shoes for signs of altered fit or excessive wear and value the contribution a skilled and experienced farrier makes to maintaining your horses’ feet in optimal condition.