SIDEBONE

Sidebone is the name given to the medical condition that results in two of the key cartilages of the horse’s foot (the collateral cartilages) hardening to become bone-like. It is a very common finding in horses, but a diagnosis that lots of horse owners are very afraid of. Yet, according to our vets, sidebone is often not something to panic about.

Here we look at sidebone in detail and discuss just how much we should panic when we hear our beloved horse or pony has developed it.

The collateral cartilages

The collateral cartilages are two pieces of cartilage - one on the inside and one on the outside of the horse’s foot. These cartilages are found just above the heel of the foot and run forwards towards the toe. They sit mostly within the hard shell of the hoof. They are attached to three of the bones in the foot (the pedal bone, and the short and long pastern bone). You can feel the cartilages as slightly squishy areas above the hoof in the heel of your horse or pony.

These cartilages are a part of the shock-absorbing mechanism of the horse’s foot. Horses and ponies are heavy animals so when they land on the ground with each foot they need a way to absorb some of the shock and force that is created. This is the job of the collateral cartilages and the digital cushion (another structure in the foot).

Sidebone

Sidebone is described as the mineralisation of the collateral cartilages of the hoof. This mineralisation makes the cartilages more bone like and rigid. If the collateral cartilages have become mineralised in this way, you can often feel the changes by feeling the hardening around the heel of the horse. Some swelling is also often seen just above the top of the hoof. Sidebone is more common in the front feet than the hind feet because the front legs carry more weight.

However, as we said in the beginning many vets are telling us that sidebone is actually not something we should panic too much about. They say that most horses with sidebone are not lame, and that if they are lame it is not because of the sidebone itself, but rather the sidebone pressing on other sensitive parts of the foot.

Predisposing factors

The following factors make horses more likely to develop sidebone:

Heavy landings on the front feet, such as is experienced in showjumping.

Poor foot balance, i.e. poor farriery.

Heavier horse breeds like the Percherons and Shires.

Poor limb conformation as this can make horses or ponies carry their weight differently.

Direct trauma to the collateral cartilages.

Diagnosing sidebone

PHYSICAL EXAMINATION

Physical examination by your vet will usually reveal hard collateral cartilages and swelling above the hoof capsule.

NERVE BLOCKS

Your vet may do nerve blocks of the heel region to numb any pain from the collateral cartilages. The problem with this method is that it also makes other structures in the area numb, so all you can see is that the heel has pain but not which structure is the main problem.

X-RAYS

X-Rays are often taken once the site of lameness has been confirmed. It is generally best to scan both front legs to allow both sides to be compared to each other.

OTHER INVESTIGATIONS

Bone scans and nuclear scintigraphy may provide more information about whether the side bone is making the horse lame or not. These tests can show if the sidebone is inflamed or not. If the sidebone is inflamed it is more likely to be the cause of the lameness.

Treatment

If sidebone is proved to be the cause of lameness, treatment starts with good farrier work to balance the foot. A common farriery technique used in these cases is to shoe the affected horses with flat, wide, webbed shoes with a rolled toe, which are wide at the quarters and heels and extend beyond the ground surface at the heels to support the heel regions and allow for expansion. Nails should not be used behind the mid-quarter of the foot.

Balancing the feet like this often makes the lameness go away. Unfortunately, the cartilage is unlikely to go back to having a normal appearance, but provided the area is not inflamed, the horse or pony should stay sound!