Anatomy and Bones of the Foot
The purpose of the hoof is to minimize concussion and support
the weight of the horse. The hoof wall is made up of
complex soft tissue and keratin (hardened protein kind of like
our fingernails but much harder. The corium, a dermo-
epidermal, highly vascularized layer between the wall and the
coffin bone, has a parallel, laminar shape, and is called the
laminae. Laminar connection has a key role in the strength
and the health of the hoof. The bone structure of
hoof starts with half of the short pastern within it and the
coffin bone which sets just below the coronary band. The
navicular bone lies behind the coffin bone and below the short
pastern. The coffin bones is shaped to a kind of a point
at the bottom and held up by thick cartiage cushions on each
side. The extensor tendon attaches at the front and
the flexor tendons attaches at the rear of the coffin bone.
Strong ligaments bind the coffin bone to the short pastern.
When the horse steps down all these help to keep the coffin
bone in place and from dropping down too low or tipping back
too much. There is a fluid filled bursa sac that
protects the navicular bone from strain and friction from
the flexor tendon moving up and down. If this bursa
blows or is injured the horse goes lame and shows signs of
navicular disease.
The Circulation of the Hoof
The hoof actually helps pump the blood back up to the heart
with each step. The hoof expands and contracts as
the horse moves and the pressure generated in stepping down
forces the blood out of the foot and and up the veins in the
leg. Then when the foot is lifted the release of the
pressure allows new blood into the foot. Since the horse
is always moving it helps to keep his feet healthy. But
those horses that are stalled and have no activity can have
a lot of foot issues if not properly excercised.
Looking Down at the Bottom of the Foot
The frog is a heart-shaped structure that extends forwards
across about two-thirds of the sole. The frog grows
from the front to the back. At the back, the frog
merges with the heel periople. In its midline, it has
a central groove called the sulcus that extends up between
the bulbs. It is dark gray-blackish in color and of
a spongey rubber consistency. It acts as shock absorber
and helps to grip on hard, smooth ground. The frog also
is the pump that moves the blood back to the heart. In
the stabled horse the frog does not wear well. It can
be susceptible to bacterial and fungal issues like foot rot.
In the free-roaming horse the frog can harden and dry up
becoming to thin, limiting circulation causing contracted
heels. The sole has a whitish-yellowish or grayish
color. It covers the whole space from the perimeter
of the wall to the bars and the frog, on the underside of
the hoof. The layer as a wax feel referred to as
'live sole'. Its surface can be variable and is
determined by the result of ground contact. If there
is no contact, as in shod hooves or when the walls are too
long or the movement poor, the lower surface of the sole
can have a shelly crumbly consistency. If the horse
has an active contact with the ground the sole can be of
very hard consistency. The front portion beneath the
front of the pedal bone is called the 'sole callus'.
The bars are the inward folds of the wall, originating
from the heels at an abrupt angle. The strong structure
built up by the extremity of the heel and of the bar is named
the 'heel buttress'. The sole between the heel walls
and the bars is named the 'seat of corn'. The bars
have a three-layer structure, just like the walls. When
overgrown, they bend outwards and cover the lower surface
of the sole.
Parts of the hoof
Parts of the hoof
Support system from long pastern to the hoof
|
Hoof Wall:
The hoof wall grows from the coronary band at the hairline down.
A healthy hoof grows at the same rate of time as the wear and
tear, broken edges, etc. Just below the coronary band is
the "periople" which is a narrow strip of cuticle like material.
It produces a waxy like substance that helps to keep the hoof
from drying out.
The Three Hoof Wall Layers:
The Pigmented Layer:
The walls are composed of three distinct layers: the pigmented
layer, the water line and the white line. The pigmented
layer is generated by the coronet, and its color is just like
that of the coronet skin from which it is derived. If
the coronet skin has any dark patch, the walls show a parallel
pigmented line, from the coronet to the ground, showing the wall's
growth direction. This layer has protective role, and is not
as resistant to ground contact.
The Water Line:
The water line is built up by the coronet and by the wall's corium
(the living tissue immediately beneath the walls). The
thickness increases in proportion to the distance from the coronet.
When it gets to the lower third of the walls, is thicker than the
pigmented layer. It is very resistant to contact to the
ground, and it serves a support function.
The White Line or Inner Layer:
The white line is the inner layer of the wall. It is softer and
fibrous in structure and light in color; white in a freshly
trimmed hoof, yellowish or gray after exposure to air and dirt.
From the underside of the healthy hoof, it is seen as a thin line
joining the sole and the walls. The white line grows out from the
laminar connections. Any visible derangement of the white line
indicates some important derangement of laminar connections that
fix the walls to the underlying P3 bone. Since the white line is
softer than both the walls and the sole, it wears fast where it
appears on the surface; it appears as a subtle groove between the
sole and the walls, often with some debris or sand inside.
The Three Layers Adjoined:
The three layers of the wall merge in a single mass and they grow
downwards together. If the wall does not wear naturally, from
sufficient movement on abrasive terrains, then it will protrude from
the solar surface. It then becomes prone to breakage, and the
healthy hoof will self-trim, by breaking or chipping off.
Normal Foot
The angle of the foot and the pastern should be the same
45 to 50 degrees in the front and 55 degrees in the hind.
Pairs of feet should match and be balanced. The foot should
fit the in size and angle of the horse's breed. The frog should
have the least amount of trimming done to it either when shod or
going barefoot. The front toe should be about 3" long from
the coronet band. The hind toe should be about 3.5" to
4" long from the top of the coronet band. From the tip of
frog to the white line should be about 2" when you pick up the
foot and look at the bottom. Watching the horse move from
the side the foot should hit the ground heel first. This is
because the shock absorbing structures are in the back of the foot.
If the horse places the foot down toe first he is protecting the
structures in the back of the foot due to soreness. Watching
from the front on a flat, level surface, the front foot should
be put down flat. The rear foot may meet the ground flat
or outside first.
Breakover
When the heels leave the ground the foot rotates over the toe.
The point on the toe that the horse "breaks over" can be seen as
an area of greater wear on the shoe, or with the bare hoof, an area
that the horse keeps neatly level and trimmed by himself.
Horsemen called it the breakover point. A healthy bare hoof
has a short toe which requires less effort to breakover. The
longer the toe, the more effort is needed to breakover, and the
greater the strain on the tendons and ligaments.
A to B - Angle of pastern
B to C - Angle of hoof
Should be Equal
Victrix #6
Dappled Isabella Palomino
Sculpted and painted by
Carol Williams 2008
Rio Rondo Enterprises
Front toes should be shorter
in length than hind toes.
Victrix #6
Dappled Isabella Palomino
Sculpted and painted by
Carol Williams 2008
Rio Rondo Enterprises
Parts of the outer hoof
|
