What is laminitis?

Diagram of a normal horse foot

X-ray of a normal horse foot

Laminitis is an extremely painful and potentially devastating condition affecting the hooves of horses.

In the foot of a normal horse, the hoof wall and the pedal bone (the lowest bone in the foot) are joined together by velcro-like tissues called laminae. One set of laminae is attached to the hoof wall, and the other set is attached to the pedal bone. These 2 sets of laminae are normally tightly bonded together, and this enables the horse to bear its full weight on its hooves rather than through the pedal bone. The equivalent for humans would be for us to bear weight on one of our fingernails!

When a horse develops laminitis the laminae become inflamed and separate, which weakens the velcro-like attachment of the hoof wall on the pedal bone. When the horse bears weight on a laminitic hoof the pedal bone can then drop downwards in relation to the hoof wall. This is called rotation of the pedal bone and is excruciatingly painful for the horse.

In extremely severe cases of laminitis the pedal bone can perforate out of the bottom of the hoof. Unfortunately, euthanasia is the only option in these cases.

Diagram of a horse’s foot affected with laminitis

X-ray of a horse’s foot with severe laminitis

Signs of laminitis

How would I know if my horse had laminitis?

Laminitis is an inflammatory condition causing pain, and therefore many of the signs associated with it are signs of pain or inflammation. Laminitis also causes the hoof wall to grow abnormally, and so other signs include irregularities in the hoof. The signs can vary in severity as shown by the table below. It should be noted that a case of mildly painful laminitis can quickly progress to a severely painful case.

Horses with laminitis will find it difficult to put their feet down, and will often adopt a ‘rocked back’ or rocked forward stance. Although, it should be noted that if all 4 feet are affected the stance may be unchanged.

If the condition goes on for some time or there are repeated episodes of laminitis in an individual horse, the damage to the laminae can become irreversible leading to rotation of the pedal bone and permanent foot pain. In many cases of this severity euthanasia becomes the only option.

Diagnosis

What should I do if I suspect my horse has laminitis?

Severe laminitis is an emergency, and ongoing ‘moderate’ disease can result in painful long-term consequences. Prompt attention and treatment as soon as the signs of laminitis are recognised will not only relieve the pain, but also reduce the long-term damage.

Seek veterinary advice
Until the vet arrives:
- Remove from pasture
- Provide deep bedding
- Ensure they can reach food (soaked hay) and water easily

When the vet arrives they will examine your horse. If they confirm a diagnosis of laminitis, they will treat the painful symptoms and make recommendations with respect to trimming, farriery, and management. The vet may also test for underlying hormonal conditions: identification and treatment of these may reduce the risk of future painful attacks and permanent damage.

Causes

What causes laminitis?

Our understanding of the cause of laminitis has improved dramatically over the last 5 years. Historically it was always thought that access to new pasture was the primary cause for laminitis, but this didn’t explain the common situation of two horses being grazed on the same field but only one developing laminitis. Clearly grazing plays an important role in triggering laminitis, but the fact that some horses are susceptible whereas others appear not to be tells us that there must be factors within each individual that affect whether or not he/she might get laminitis. So what are these factors?

90% of laminitis cases however have an underlying hormonal cause, and it is this hormonal cause that determines whether they will develop laminitis when they are turned out onto new pasture.

The exact mechanisms whereby hormonal diseases cause laminitis is currently unknown, but what we do know is that there is a complicated interplay between three hormonal conditions called PPID, EMS and insulin resistance which increases the risk of an individual horse developing laminitis.

An individual horse can have EMS and PPID concurrently, and therefore it is usually worth testing for both conditions.