Page 281 - The Veterinary Care of the Horse

and the bone.

• Degenerative changes occur within the bone substance.
VetBooks.ir • The supporting ligaments may tear at the site of attachment to the navicular bone.

The pain arises from within the bone and from strains and sprains to the surrounding soft
tissues. Navicular bone pain may be associated with poor drainage of blood from the vessels

and spaces in the bone marrow leading to raised pressure and distension of the small veins
within the bone.

Clinical signs

CHANGE IN ACTION

Over a period of time there is a gradual loss of performance and shortening of the horse’s
stride. The toe is often placed on the ground first to reduce concussion at the heel and

pressure on the navicular bone and DDFT. This gives a stiff, ‘shuffling’ gait and the horse
may have a tendency to trip or stumble.

LAMENESS

Lameness is insidious in onset and only rarely occurs suddenly. It is usually bilateral but if
the changes are more advanced in one limb, this leg will show the lameness first. In the early
stages the lameness is slight and intermittent, tending to improve with exercise. It is most

obvious when the horse works on a circle with the lame limb on the inside, especially when
lunged at trot on a hard, flat surface. The horse often holds its neck and head rather stiffly

and turned to the outside of the circle in an attempt to reduce the weight taken by the inside
forelimb. Affected horses may become reluctant to jump or to increase their length of stride.

The degree of lameness increases as the disease progresses and eventually the horse is
continually lame.

SYMPTOMS OBSERVED AT REST
These include the following.

• Shifting the weight from one front foot to the other.

• Standing with one foot in front of the other with the heel slightly elevated; this relieves
the pressure between the DDFT and the navicular bone and is known as ‘pointing’ the

foot. When both feet are painful they are alternately pointed (Figure 6.54).

• Digging a hole in the bedding and standing with the toes in the hole and the heels raised
on the edge.