Page 294 - The Veterinary Care of the Horse

The function of the cartilages

Together with the digital cushion they are believed to play a part in absorbing harmful
VetBooks.ir concussion at the back of the foot. When the horse takes a stride and the foot contacts the

ground, the frog is pushed upwards into the digital cushion and this forces the cartilages
outwards. At the same time, downward movement of the pastern due to the weight of the
horse has the same effect. The resultant changes of pressure within the foot are important for

assisting the flow of blood through the cartilages.

Causes

This may be a normal ageing change. The process can be accelerated by increased
concussion due to:

• mediolateral foot imbalance

• conformation abnormalities, e.g. toe-in horses tend to develop sidebone on the lateral
side of the foot

• poor trimming and shoeing.

Ossification can also be caused by a direct injury, e.g. a wire cut to a lateral cartilage.

Clinical signs

Sidebone very rarely causes lameness. The condition develops slowly over a period of time
and is usually discovered when the foot is palpated and the hardened cartilages are felt.

When it does cause lameness:

• the lameness is gradual in onset

• it is more obvious on hard surfaces
• there is occasionally heat over the affected area

• pressing the affected cartilage may cause pain

• fracture of an ossified cartilage can cause sudden-onset lameness.

Diagnosis

The diagnosis of sidebone is not always straightforward as there is no nerve block that
selectively desensitizes that part of the foot. Many horses that are not lame have extensive

mineralization of their lateral cartilages that can be seen on X-ray (Figure 6.59). Scintigraphy
may be helpful in determining if there is any active remodelling of the cartilages.