Page 618 - The Veterinary Care of the Horse

area and aggravating the injury. However, sustained overactivity of these nerve cells, known

as facilitation or wind-up, is harmful as the sensation of pain can be generated from stimuli
VetBooks.ir such as light touch. Pain may also continue to be felt after the injury has healed.

It is believed that tissue has a pain memory and that repetitive insults can lead to a lower
threshold to the perception of pain and faster onset of wind-up which can occur after just 45

minutes of painful stimulation.
An example may help you to understand the concept of wind-up, which can occur with

sensory nerve endings in the skin as well as within the spinal cord. Have you ever purchased
a new garment and been slightly irritated by a label contacting the skin? The initial sensation

is one of mild irritation rather than pain. However, if the label is not removed, the stimulus is
perceived as increasingly painful and the area will become inflamed. The stimulus itself has
not changed but sensitization of the nerve endings in the skin due to repeated stimulation

make it feel very sore. This soreness can remain some time after the garment is removed.
Imagine then the discomfort of the horse that has to tolerate an uncomfortable saddle,

numnah or rug. Horses that dislike the front of their rugs being done up or undone have often
been sensitized by the scratchy nature of worn velcro fastenings.

Facilitation of the spinal cord also influences the outgoing nerve signals to skeletal

muscles, causing alteration in muscle tone. This in turn affects the range of motion of the
joints and the way the horse moves.

Nerves from the musculoskeletal system share common pathways from the spinal cord to
the brain with nerves from the organs of the body. As a result, pain from the internal organs

can influence the muscles and vice versa. This is why practitioners of acupuncture,
osteopathic and chiropractic treatments undertake a complete and holistic examination of
their patients, rather than focusing immediately on the apparent problem.

What happens during the examination?

• A detailed history will be taken. Consideration will be given to previous injuries as well

as the current complaint.
• The horse will be examined at rest. The practitioner will assess the conformation, stance

and muscle development of the horse. Any abnormal wear pattern on the shoes will be
noted.

• The horse is examined at exercise. While the horse is walked and trotted in hand, its
movement, stride length and foot placement is assessed. The horse is then observed

turning in a small circle. If it is considered necessary, the horse will be seen on the lunge
or ridden.