SHOCK ABSORBER IN HOOF

1. SHOCK ABSORBER IN
HOOF

2. The Hoof as Shock Absorber
• The shock of concussion is dissipated laterally against
the hoof wall
• As the foot strikes the ground, downward pressure
flattens out the concave surface of the sole
• This distributes weight laterally against the hoof wall,
which expands about a quarter of an inch (6mm)

3. The Hoof as Shock Absorber
• With heel pressure, the frog compresses the digital
cushion, which then flattens and pushes the lateral
cartilages outward in opposite directions
• During concussion the navicular bone shuttles the load
from the digital cushion through to the short pastern
bone, bypassing the coffin bone and relieving some of
its load
• The conformation of the knee and hock joints also helps
reduce the shock of impact

4. Internal Hoof Anatomy
The Elastic Tissues
 Elastic tissues are those which are capable of changing
shape in response to foot impact
 The elastic tissues are:
 The digital cushion
 The hoof wall
 The sole
 The frog
 The bulbs of the heel

6. The Digital Cushion
– Is the main shock absorber of the
hoof
– Is bound by the lateral cartilages at
the sides, the deep digital flexor
tendon above, and the horny frog
below
– The back of the cushion forms the
bulbs of the heel

7. • The digital cushion is a wedged-shaped structure with
a fibro-fatty composition in the foal and in the colt,
and it hardens into a fibrocartilagineous tissue in the
adult horse. It is very elastic and has very few blood
vessels and nerves.
• It is located in a wedged-in position between the
lateral cartilages on the side, then deep flexor tendon
on the top and the frog on the bottom and rear. It
separates the frog and the bulb from underlying
tendons, joints, and bones, providing cushioning
protection.

8. • When it is compressed by the pastern bones and
frog, it absorbs shock and cushions the bones. As
weight is placed on the hoof, pressure is
transmitted through the phalanges to the wall and
onto the digital cushion and frog. The frog, a
highly elastic wedge-shaped mass, normally
makes contact with the ground first. The frog
presses up on the digital cushion, which flattens
and is forced outward against the lateral
cartilages. The frog also is flattened and tends to
push the bars of the hoof wall apart. When the
foot is lifted, the frog and other flexible structures
of the foot, such as the digital cushion, return to
their original position.

10. “The presence of a moderate to large
amount of elastic fiber profiles in the
DIGITAL CUSHION, with its high
resilience, may allow the elastic fibers
to support the tensile strength of
collagen bundles,” he explained.
“Elastic fiber-rich dynamic tissues are,
therefore, able to deform and store
energy under normal physiological
loads and use this energy to drive
recoil back to a resting state.

11. • There are significant inconsistencies in previous
reports describing the composition of the DC. One
study stated that the DC is composed of only
elastic fibers and adipose tissue . Another study
examined the histology of the DC and reported
that the equine DC consists primarily of tightly
packed collagen fibers with only a few
interspersed elastic fibers and very little adipose
tissue . A more recent study indicated that the DC
contains connective and adipose tissues, elastic
fibers, and tissues with matrix rich in hyaluronic
acid . Collectively, these studies disagree about
the architecture of the DC. Such differences might
be due to variability in sectioning techniques and
can partially be explained by examining the
distinct regions of the DC.