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TENDON INJUR I ES
SUMMER 2014 ISSUE
The long tendon which runs down the back
of a horse's cannon bone is called the
superficial digital flexor tendon (SDFT).
This tendon acts as a spring to store and
release energy during fast exercise, and is
the most commonly injured tendon in the
horse. Laboratory testing has shown that the
SDFT can be stretched to 15-17% before it
is damaged. However other tests have
shown that during galloping a horse's SDFT
is naturally stretched by 16%, putting it at
immediate risk of tearing. Therefore if
significant microdamage has already
occurred weakening the tendon, any
additional stretch of the tendon - an
abnormal loading event - could cause a
strain to occur.
There are many possible reasons for an
abnormal loading event, but they generally
include fast galloping, landing awkwardly
after jumping, working on an uneven surface,
abruptly sliding to a stop in the field or
spooking at a plastic bag. In summary
anything where the tendon is stretched
beyond its natural limit. Many of these we
cannot predict or do anything about, but
there is one that we can - tiredness.
During exercise, part of the weight-bearing
load going through a horse's leg is absorbed
by contracting muscles, and the rest by
stretching tendons. When a horse exercises
to the point of tiredness, its muscles fatigue
and are therefore less able to contract and
take up their share of the load. If the exercise
then continues, the tendons must take up the
part of the load which the muscles cannot,
stretching them beyond their limit, and a
strain occurs. We can of course do
something about this. Obviously we would
stop riding a horse which is exhausted,
but we should give special attention to
horses and ponies coming back to work
after a lay off. They will have lost their
fitness and therefore their muscles will
fatigue more easily, giving a higher risk
of tendon injury.
An ultrasound image of a core lesion
within a tendon
What causes microdamage to progress
to serious strain?
tendon injuries are common
in horses, particularly those
used competitively. The tendon
most commonly injured is the
superficial digital flexor
tendon (SDFT).
In summary...
A bowed tendon in the left hindlimb
EQUINE MATTERS
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