Splints in horses

What is a splint?

Broadly speaking, splints are hard lumps that build up on the side of the cannon bone (front or back).

To get a better idea of what a splint is, let's take a brief look at the anatomy of a horse.

The region generally known as the cannon is made up of a few different parts:

The main metacarpal (anterior) or metatarsal (posterior) bone
The rudimentary metacarpal/metatarsal bones, on either side of the main bone, that support and strengthen it.
The fetlock flexor tendons (superficial and deep)
The fetlock suspensory ligament, directly linked to the rudimentary bones.

Splints are generally brought about by swelling of the outer layer (periosteum) of a long bone. This swelling leads to the formation of a bone callus (bone remodelling), the splints.

More often than not, the splint will be on the inside of the forelegs, but it isn’t uncommon to find one on the outside and/or on a hind leg.

Splints usually show up on the cannon bone, even though they can show up on any bone in the body, despite not being as common. They can show up on the inside or outside of the pastern, on the radius, the tibia as well as the bones of the skull.

Causes of splints

There are a number of reasons for the swelling that causes splints. These can vary depending on the situation. Remember that splints are "hard lumps". The following are the main causes of splints:

1- Trauma-induced splints

This is one of the most common causes of splints in horses. There are two types of trauma injuries:

The horse "kicks" itself with the opposite leg, injuring the inside of the other leg.
The horse is kicked by another horse; in this case the outer part of the horse could be injured.

Regardless of the "side" injured, if it’s trauma-related, the splint might show up on the main bone or one of the rudimentary bones.

Bear in mind that, in cases such as this, one of the rudimentary bones could be fractured from the impact. In this case, the splint could be even more severe if the fracture isn’t treated properly.

2- Splint caused by damage to the fetlock suspensory ligament

This type of splint is down to damage caused to the suspensory ligament between the main and rudimentary metacarpals that, in turn, causes calcification.

This type of splint could be caused by an untreated misalignment or an overstretched ligament. Note that the suspensory ligament tends to calcify naturally as the horse ages.

3- Growing splints

As young horses grow, their frame undergoes significant changes. Splints might show up during growth spurts. Bear in mind that they could just be temporary adaptations of the frame and that these splints will more than likely go away in adulthood when the horse has stopped growing. Having said that, all early-onset splints should be checked out by a vet.

Symptoms of splints

There are no one-size-fits-all symptoms of splints, as they depend on where they are and how sensitive the horse is.

Remember that splints don't always cause lameness in horses, not to mention that the symptoms of lameness can also vary in intensity.

Also bear in mind that, when it comes to splints, there are two phases; each of which has their own symptoms:

Acute phase

This is when swelling is at its peak. The "classic" symptoms of a swollen area are: pain, heat, redness and swelling.

During this phase, lameness will be noticeable and is directly linked to the swelling. The splints will also be painful when pressure is applied. The area around the splint might also be swollen.

Chronic phase

Once the swelling has subsided and the splint has "settled in", lameness linked to an inflammatory process will go away. The splint is said to be "in position".

Get the horse treated if it’s still showing signs of lameness, whether permanent or transient. In this case, it would be secondary lameness because it isn't directly linked to the splint but to the knock-on effect.

For example, if the splint is close to the fetlock's suspensory ligament and rubs against it, this can cause damage to the ligament (desmite), which is a cause of lameness. This lameness will be linked to the horse's activity, which causes more friction. When the horse is rested, the lameness will be less severe.

Although there is no one-size-fits-all rule, broadly speaking, the lower the splint (close to the fetlock) and the further back (close to the tendon), the greater the risk of secondary lameness. What's more, when it comes to splints in the same place, the larger the splint, the greater the risk of lameness.

Diagnosing splints

Get in touch with your vet if you think your horse has a splint. The vet will normally diagnose the splint after looking at an X-ray. This will enable your vet to look at the splint from an objective point of view.

In fact, your horse might not have a large external deformity visible to the naked eye, although the internal deformation of the bone could be severe.

On the other hand, a very large deformation seen from the outside does not always mean a very large splint. This is the case for splints that are in the early stages.

Treating splints

Once the splint has been diagnosed, your vet will offer advice on the best way to treat the condition.

The earlier the splint is treated, the more likely it is to stop getting bigger. The treatment prescribed by your vet will limit bone proliferation as much as possible, and, in turn, any rubbing on the suspensory ligament.

Broadly speaking, splints are treated with anti-inflammatory drugs administered orally/locally and resting is recommended. Non-steroidal anti-inflammatory drugs are administered orally and corticoid-based gels are applied locally.

If anti-inflammatories don’t work, your vet might suggest other treatments or ways to look after it:

Cryotherapy: the results are quite impressive, although this treatment only "stabilises", it doesn’t make it smaller. Note that this technique can leave a "mark" on the treated area, resulting in the hair growing back white.
Farriery: if the splint is down to being out of alignment, this is where the farrier plays a key role. Broadly speaking, they’ll try to take weight off the hoof wall and encourage it to load the outside heel to prevent splints from developing.
Surgery: this is often the vet's last resort because quite often splints still come back. The technique gets rid of any excess bone, but as it heals, it could react by growing back a splint. Broadly speaking, surgery is opted for when there is severe discomfort in the suspensory mechanism.

Preventing splints

There are different ways to prevent splints. Here are the main ones:

The right diet for growing horses

To ensure that your horse grows properly and that its skeleton develops in the best way possible, it needs to be given the right amount of food. Particular attention should be paid to minerals, trace elements and vitamins, in particular the calcium-to-phosphorus ratio, which is of the utmost importance for bone metabolism.

As well as taking in the right amount of minerals, remember to limit the amount of starch per meal, as this could lead to conditions such as osteochondrosis.

Keep track of weight

Keeping track of the horse's weight over the course of its life is of the utmost importance. Overweight horses will "overload" their legs, in turn, leading to overuse. What’s more, this overstretches the horse’s joints, which can lead to osteoarthritis.

Keep track of alignment

It’s important that farriers or handlers monitor whether the horse is out of alignment on a regular basis.

Cooperation between the vet and the farrier can minimise the risk of splints in horses that are out of alignment.

Restrict how much exercise young horses get

Physical exertion in young, growing horses can negatively affect the frame. This is why racehorses are more prone to splints than horses that have been worked progressively, because their frames have been stressed when they weren’t as strong as older horses.

Protect the legs

There is no shortage of leg protectors on the market that will limit trauma and, in turn, reduce the risk of injury. The type of protection and the frequency of use can be adapted depending on the horse and the discipline.

So, as you can see, splints are fairly common in horses. If properly treated, there’s no reason they should hold back your horse's career. If you think your horse is suffering from splints, get in touch with your vet as soon as possible, as early treatment offers the best chance of cure.

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