Page 252 - The Veterinary Care of the Horse

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Figure 6.40a and b Pedal bone prolapsing through the sole of the foot: a) prolapsed pedal bone; b) the pedal bone has
penetrated the sole (right), and a crescent-shaped area of imminent prolapse can be seen

The disease can be divided into 3 stages:

1 The developmental phase – this is the time when changes in the laminae begin but the
horse is not yet showing any signs of pain.

2 The acute phase starts as soon as the pain begins and continues until the pedal bone
starts to move within the hoof capsule.

3 The chronic phase includes all the possible subsequent outcomes from mild ongoing

lameness to severe pain and penetration of the pedal bone through the sole of the foot.

The important thing to remember is that by the time the horse or pony is showing signs of
lameness, damage has already occurred within the laminae and prompt action should be

taken to minimize the progress of the disease.
Our understanding of laminitis is increasing all the time. Whereas it was traditionally

associated with eating too much rich grass, it is now known that the majority of animals with
laminitis have underlying hormonal conditions, which make them particularly susceptible to

the disease. These include pituitary pars intermedia dysfunction (PPID, also known as
Cushing’s disease) and equine metabolic syndrome (EMS). Both of these diseases interfere

with the normal metabolism of insulin and this is known as insulin dysregulation (ID).
Laminitis can also be triggered by sepsis (severe infection) or excessive weight-bearing on
one limb, together with a number of other causes, which will now be looked at in more detail.