A horse or pony with a splint injury is likely to be in pain and will often lead to them showing signs of lameness.

Understanding splints and how to diagnose them is an important part of caring for your horse.

Many owners will routinely carry out an inspection of their horses legs prior to each ride, looking for any heat, swelling or any rigid bumps in the splint area of the leg and whether the horse feels any pain when touched. 

In this article we look at what the splint bone is, how best to diagnose if your horse has developed a splint injury and what you can do to treat the injury if it does occur.

Where is the splint on a horse?

On each side of a horses cannon bone are two small bones known as the splint bones. These two bones - the medial and lateral splint bones - are in fact the remains of the horses prehistoric ancestor which had multiple toes and these splint bones are thought to be remains of the second and the fourth toes. 

Between the cannon bone and these two small splint bones is a ligament, known as the interosseous ligament. 

As a horse gets older (normally between the age of 3 to 5) the ligament and two bones ossify and become one. Because of this, splint injuries are more commonly found in younger horses between the ages of 2 and 5.

During the ossification process a young horse may sometimes experience inflammation and swelling within the ligament itself which can lead to them experiencing pain and be further irritated by jumping, running or working the horse. Lameness created by splints at this age is most obvious in trot and will often come and go.

As the ossification process ends and the ligaments and bones fuse together injuries are less common and rarely occur in horses over the age of 5. 

Splint injuries are often found in the front legs and are rarely seen in hind legs.

The majority of splint injuries occur on the medial side (inside) of the forelimbs as the medial splint bone on the inside of the leg has a flat surface and when weight is transferred to the bones the medial splint bone bears more weight that the slanted surface of the lateral splint bone. 

FUN FACT: The earliest known ancestor of the modern day horse is known as a Eohippus or “Dawn Horse” which became extinct at the same time as the dinosaur. 

What causes a splint injury? 

An injury to a splint, often referred to as “popping as splint”, occurs when the interosseous ligament is damaged. Injuring this ligament will result in inflammation and pain and an increase in heat within the area.

As well as through a direct trauma or injury a horse with poor conformation, unbalanced hooves, a mineral imbalance in their diet, being overweight or repeated work on hard and uneven ground can also lead to splint injuries and complications.

‘False splints’ are also common and are a direct result of an external trauma to the splint bones themselves, often through a kick or fall which then leads to inflammation of the splint bone itself. This can also lead to fractures in the splint bones.

Diagnosing a horses splint injury

Thermal Imaging is a useful diagnosis tool when a horse has developed a splint injury. As the injury will show an increase in heat, using thermal imaging technology can show exactly where the issue has occurred providing the best opportunity to support the healing process.

Traditionally your vet may look towards an x-ray being done if they suspect a fracture has occurred. If your horse has an open wound or visible bruising from a kick then a fractured splint should be suspected and diagnosed prior to any treatment program is designed. Ultrasounds can also be useful to detect the specific injury to the ligament itself.

Once a professional diagnosis has been done a rehabilitation and recovery plan will be required alongside a period of box rest.

Treating splint injuries in horses

In the majority of splint injuries horses will respond to a period of rest and recuperation, often with a bout of anti-inflammatory treatment to assist in the reduction of inflammation within the ligament or bone itself.

Professional diagnosis and involvement from your vet will be required, so a splint injury is likely to be expensive to treat but is also likely to be covered under your pet insurance plan.

NSAID anti-inflammatory medications (such as Bute) are widely used immediately after the injury occurs, however, with owners and vets now well aware of the long term side effects and complications created by NSAIDs many owners look towards more long term and natural forms of therapy.

Your vet may recommend a topical anti-inflammatory cream which is rubbed into the effected area, applying cold therapy such as ice boots or using the latest advancements in magnetic technology to help speed-up the recovery process. Key to 'stage one’ of the rehabilitation is reducing the inflammation and ensuring the horse is rested and not bearing too much weight on the effected leg. In most cases the heat within the splint will reduce with a few weeks.

Hydrotherapy can be a useful form of complementary treatment to support the horses recovery process along with regular compression bandaging of the affected area. 

Fractures to the splint bones are generally more serious and can sometimes require an operation, particularly if the fracture occurs towards the top end of the splint bone. Plates and pins can be used in some cases to stabilise the fractured bone but fractures to the middle of the splint bone are commonly uncomplicated and will generally resolve themselves with a period of rest and rehabilitation.

The length of rest and rehabilitation required depends on the individual case and the main complication is often the amount of time required which can take months and even longer in older horses. A sports horse whether taking part in barrel racing, showjumping, eventing or polo will not be able to compete until the splint is completely healed. In the majority of cases a period of rest between 10 and 12 weeks will be required.

Once the splint has healed and the horse can return to work it is crucial that you keep an eye on the injury and go slow with the horse; rushing it back too soon could create further complications.

In summary

Continuous inspection of your horses legs is a great way to protect your horse from a splint injury. Prevention is as important as cure and detecting lameness early may help to avoid splint injuries.

If your older horse (over the age of 5) develops splints this can result in higher levels of lameness and will require extended periods of rehabilitation than with younger horses. It may also lead to arthritic issues within the joint itself. 

Ensuring your young horse is warmed up properly before exercise is important as well as maintaining proper foot trimming and shoeing. If your horse is active or a sports horse then using exercise or brushing boots can help prevent impact injuries and if your horse does develop signs of a splint injury contact your vet as soon as possible.