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Finding your horse “fracture lame”, with a sore and badly swollen leg, is the stuff of nightmares. While the worst-case scenario always tends to spring to mind, there could be another reason for this sudden and dramatic development.

“With horses, there are basically three things that look like a broken leg,” says Gil Riley MRCVS, of Pool House Equine Vets. “One is a broken leg, of course, and another is pus in the foot.

The third possibility is a condition referred to as cellulitis, often associated with another condition, lymphangitis.

“Cellulitis is an inflammation of the tissues under the skin, most commonly caused by a penetrative wound or a skin infection, while lymphangitis is an inflammation of the fine vessels that drain tissue fluid from the limb,” explains Gil. “Both can cause a characteristic ‘elephant leg’, typically a hind limb, along with lameness that can be so severe that the horse is unwilling to weight-bear.”

Gil explains that the conditions can develop in tandem, creating a scenario that’s challenging to treat.

“The lymphatic vessels are muscle-less tubes that rely on the flexion and extension of the limb to pump fluid back up to the body,” he says, describing a “spaghetti junction” of these vessels at hock and thigh level. “If cellulitis spreads to the lymphatic system, the tubes become inflamed and narrowed and cannot carry fluid away. They will also produce inflammatory fluid themselves, further contributing to fluid build-up and making the horse so uncomfortable that he does not want to move. The natural pumping action within the limb then fails, the leg balloons and the situation snowballs.”

Prompt action is vital, whether one or both conditions occur.

“Treatment must be immediate and aggressive, because any scarring within the lymphatic vessels can leave the leg more prone to the problem in the future,” says Gil. “Large doses of anti-inflammatories — either steroidal or non-steroidal, or both together — are usually given, along with robust broad-spectrum antibiotics to target the infection.

“A walking programme must start as soon as the horse is comfortable; this helps pump the fluid back up the leg and the antibiotics down it, reversing the vicious cycle that has led to the swelling and pain.”

Repeated flare-ups

Scratches and small wounds are more likely to go unnoticed in winter and are an ideal entry-point for bacteria. However, infection may be “haematogenous” — originating in or carried by the blood.

The cause may not be obvious, as in the case of Pauline Jaggs’ dressage horse Rosenfee. After coming in from the field in January with an extremely swollen hock and hindlimb, the mare developed such severe infection that she was hospitalised on multiple occasions over several weeks.

“Every time she came home, the cellulitis flared up and she would be fracture lame again,” says Pauline, who was aware that Rosenfee might not recover. “Luckily, she did at last improve and we could start walking her in-hand, building it up from a few minutes at a time.”

The mare was back in the dressage arena in August and is now winning at advanced medium level.

Ref Horse & Hound; 15 December 2016