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Lecture – The Equine Hoof
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The Equine Hoof
EQS 110
Lecture – The Equine Hoof
Return to Table of Contents
Table of Contents
Functions of the Hoof.................................................................................................................... 3
Basic Structure of the Hoof .......................................................................................................... 3
Skeletal Components of the Hoof ............................................................................................... 3
Sensitive and Insensitive Structures of the Hoof ........................................................................ 4
Sensitive Structures ................................................................................................................. 4
Insensitive Structures ............................................................................................................... 4
Anatomy of the Hoof ..................................................................................................................... 5
External Hoof Anatomy – Hoof Capsule .................................................................................... 5
Hoof Wall ................................................................................................................................ 5
Laminae............................................................................................................................... 6
Coronary Band ......................................................................................................................... 6
Periople .................................................................................................................................... 6
External Hoof Anatomy – Solar/Ground Surface ....................................................................... 7
Sole .......................................................................................................................................... 7
Frog .......................................................................................................................................... 7
Bars .......................................................................................................................................... 8
Heel Bulbs ............................................................................................................................... 8
Internal Hoof Anatomy ............................................................................................................... 9
Digital Cushion ........................................................................................................................ 9
Lateral Cartilages ..................................................................................................................... 9
Blood Flow of the Hoof ............................................................................................................... 10
Management of the Hoof – Thrush & Abscesses ..................................................................... 11
Thrush........................................................................................................................................ 11
Abscess ...................................................................................................................................... 12
Diagrams of the External Hoof .................................................................................................. 13
Self-Knowledge Checks .............................................................................................................. 14
Answers ..................................................................................................................................... 15
Glossary ....................................................................................................................................... 16
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Lecture – The Equine Hoof
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Functions of the Hoof
The equine hoof is a complex and strong structure that must
bear the weight of the horse and concussive forces during
exercise. There are five main functions of the hoof:
Provide a weight bearing surface
Protect the sensitive internal structures of the foot
Maintain moisture in the foot
Provide grip/traction
Act as a shock absorber
Basic Structure of the Hoof
In order to carry out the functions presented above, the hoof is comprised of both skeletal and
non-skeletal components. We will look at hoof structure and anatomy in great detail in order to
better understand its ability in facilitating locomotion and support.
Skeletal Components of the Hoof
There are three bones that are within the hoof capsule, starting most proximal to distal:
Distal end of the Middle Phalanx (P2/Short Pastern)
Distal Sesamoid (Navicular Bone)
Distal Phalanx (P3/Coffin Bone/Pedal Bone)
In order for locomotion (movement) to occur, these bones
are connected by joints, ligaments, and tendons, many of
which we discussed in the previous lecture on connective
structures:
Coffin Joint – synovial joint within the hoof capsule
Deep Digital Flexor Tendon (DDFT) – attaches to
the bottom of P3, allows the leg to bend or flex
One connective structure that we will add to this
discussion is the common digital extensor tendon. This
tendon attaches to the top/front of P3 and allows the leg
to straighten/extend.
Due to a hard cavity (hoof wall) surrounding these
components, issues with the hoof’s musculoskeletal
components can be difficult to treat.
Lecture – The Equine Hoof
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Sensitive and Insensitive Structures of the Hoof
In addition to the skeletal components of the hoof, there are also sensitive and insensitive structures
within the hoof capsule that play a vital role in maintaining the main functions of the hoof.
Sensitive Structures
Sensitive structures lie underneath the hard, outer portion
of the hoof and contain many nerve and blood vessels. Also
referred to as corium, sensitive structures are named
according to the insensitive structure it underlies and
produces. For example, the frog corium (sensitive) lies
below and produces the insensitive frog, which is what we
visibly see when we clean out a horse’s hoof. Damage to
the sensitive structures of the foot can result in poor
development and growth of the corresponding structure.
Insensitive Structures
Insensitive structures are referred to as horny layer structures.
Insensitive structures of the hoof are those that are exposed (we
can see), such as the wall, bars, sole, frog, etc.
Frog Corium (Sensitive)
Note the visible blood vessels Insensitive Frog
Lecture – The Equine Hoof
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Anatomy of the Hoof
We can categorize the various anatomical structures of
the hoof into two distinct categories:
External Anatomy
Internal Anatomy
External hoof anatomy consists of the hoof capsule and
the solar (bottom) surface; these are all the structures
that we can see and touch. Internal hoof anatomy
consists of those structures within the hard hoof capsule, many of which are elastic and help
absorb concussive forces.
External Hoof Anatomy – Hoof Capsule
Hoof Wall
The hoof wall is a multi-layered structure that functions to house and
protect the sensitive inner foot, support weight, resist wear, conduct
moisture and absorb shock. Externally, the hoof wall is divided into
three regions:
Toe
Quarters (Medial & Lateral)
Heel
A horse’s hoof wall is thickest at the toe and thins toward the heel.
The growth of the hoof wall begins at the coronary
band. A horse grows approximately 0.25 (1/4) inch
of hoof wall per month but this can vary; growth
tends to be slower in cold or dry environments.
Lecture – The Equine Hoof
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Laminae
While the hoof wall looks like a relatively rigid,
inelastic structure, it actually has the ability to
expand around ¼ of an inch when contacting the
ground. Its ability to expand, absorb shock, and
support weight is due to laminae, which are “leaf-
like”, interlocking structures found on the
innermost layer of the hoof wall. Laminae are
responsible for attaching the hoof wall to the
coffin bone; this attachment is so strong that
laminae are able to sustain 2,000 pounds of force
landing on each forefoot during a running stride!
With the laminae junction absorbing up to 67% of
the impact force, they, unfortunately, weaken over time due to repetitive stress and/or disease.
This can result in inflammation, pain, and coffin bone instability, which are signs and symptoms
associated with laminitis.
Coronary Band
The coronary band is a rim of tough, vascular specialized skin
that is the primary source of growth and nutrition for the hoof
wall. It helps produce components of the outer hoof wall as
well as being a band of support to add strength to internal
structures. Damage to the coronary band can have a serious
negative effect on hoof growth and development, with severe
cases resulting in permanent disfigurement of the hoof.
Periople
The periople is found just below the
coronary band and it provides a protective
covering for newly formed hoof wall.
Lecture – The Equine Hoof
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External Hoof Anatomy – Solar/Ground Surface
Sole
The sole is a thick plate of flaky horn that covers most the
solar surface, also called the ground (bottom) surface. Its
job is to protect the sensitive structures underneath it. A
common misconception about the sole is that it should
bear weight, but this is highly incorrect – the sole of the
horse is not designed to be constantly bearing weight from
the ground surface! If this occurs or if it hits a hard
structure (such as a rock) it can become bruised, resulting
in lameness.
When we discuss the sole we also have to mention a
structure called the white line. The white line is the
junction between the wall and the sole. The role of the
white line is to seal off the internal hoof from bacterial
infiltration. Improper care of the hoof can result in white
line disease, which weakens the white line, potentially
exposing it to bacteria.
Frog
The frog is a wide, thick, triangular-like structure that sits in the
middle of the hoof’s solar surface. It aids in protecting the sensitive
structures that sit underneath, providing traction, assisting in
circulation, and absorbing shock. On each side and in the middle of
the frog is a groove, called the collateral groove or collateral sulcus
(see above image). Special attention must be made to cleaning out
these grooves when picking the feet, as they can become invaded
with dirt, debris, and bacteria. An unhealthy frog is vulnerable to
infection that can result in severe lameness!
Lecture – The Equine Hoof
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Bars
On the solar surface of the hoof, the bearing edge of the hoof wall is visible as well as the bars.
The bars are an extension of the hoof wall that adds strength to the heel area.
Heel Bulbs
A horse’s heel bulbs are located towards the back of the hoof and are similar to the fleshy part
of the palm of your hand. This particular structure is vulnerable to bruising as well as injury
since it is not protected by the hard hoof capsule.
Lecture – The Equine Hoof
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Internal Hoof Anatomy
Digital Cushion
The digital cushion is the main shock absorber of
the hoof. It is located behind the coffin bone and
plays a vital role in the transfer of blood in the
foot. When the foot does not function properly or
is not exercising enough, the digital cushion can
atrophy, becoming “fatty” rather than “springy”,
which reduces its shock absorbing capability.
Lateral Cartilages
The lateral cartilages encapsulate the back of the coffin bone and act like a hammock to provide
resistance as the coffin bone descends when bearing weight. Competitive injury and repetitive
trauma can cause the lateral cartilages to ossify (change into bone), which can then restrict
their ability to support and reduce shock.
Video Clip – Good vs. Bad Digital Cushions
Lecture – The Equine Hoof
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Blood Flow of the Hoof
The strength of the hoof depends on nourishment from good
circulation and vascularity. The horse is a unique animal in
that there are no muscles in the lower leg or hoof to aid in
the return of venous blood back to the heart. Therefore, the
hoof and its structures have to assist in this mechanism.
Circulation of blood to and from the hoof is dependent on:
Activity
Hoof balance
Nutrition
Horses are designed to be in a constantly moving state, which promotes
good circulation. In situations where a horse is not able to freely roam
(such as the racehorse), we must incorporate activity via exercise, hand
walking, or turnout to assist blood flow to and from the hoof.
In addition to activity, the hoof must also be engaging its external solar
surface. A hoof that is balanced will appropriately engage its solar
surface whereas a hoof that is unbalanced (higher on one side then
another, too long in the toe, too high in the heel, etc.) will not.
Maintaining a routine schedule with your farrier for trims and shoeing
(if needed) will be key to keeping the hoof balanced. The surface that
your horse stands on will also impact his ability to engage the solar
surface; a footing that “cups” the hoof is ideal (such as shavings or
sawdust) while hard, concrete-like surfaces are not.
Lastly, the nutrition that your horse receives will have an overall effect
hoof health and thereby, circulation.
An Unbalanced Hoof
Lecture – The Equine Hoof
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Management of the Hoof – Thrush & Abscesses Taken in part from Hoof Care for Racehorses” by T.A. Landers, April 30th, 2011
Everyone involved in the care and management of a horse has a role in maintaining appropriate
hoof health. Poor management of the hooves can lead to disease and lameness, which can
result in days lost in training and setbacks from racing, in addition to pain and discomfort felt by
the horse. Consistent, daily cleaning of the hooves, providing the horse with sanitary living
conditions, and routine farrier care are all vital to your horse’s hoof health. Unfortunately, not
all caretakers are diligent in these measures or there are hoof ailments that no matter how
persistent you are, still occur. With a foundation of hoof anatomy knowledge, we will look at
two of the most commonly seen hoof ailments – thrush and abscesses.
Thrush
Thrush is a bacterial infection affecting the frog
(particularly the collateral grooves/sulci) on one or
more feet. This issue is generally caused by general
neglect of the feet – allowing the horse to stand in
unsanitary conditions such as manure-filled and urine-
soaked stalls and paddocks. Extremely wet outdoor
living conditions and excessive frog growth due to
infrequent trimming may also contribute to thrush.
Diagnosing thrush is extremely clear from clinical signs
– the most obvious symptom is a foul odor, but other
symptoms include extensive moisture of the frog, heat, and a thick, black discharge from the
grooves. In severe cases, a horse may be lame and/or have a systemic bacterial infection.
Thrush is an easily curable ailment if treated as soon as it is diagnosed.
Depending on the severity, you may need your farrier to remove all dead frog
tissue, followed by washing the bottom of the foot thoroughly with warm
water and a mild disinfectant such as Betadine, and then applying a liquid
thrush remedy that will help clear out the bacteria. Less severe cases may call
for just a thorough cleaning of the foot, followed by application of a liquid
thrush remedy for 3-5 days or until the issue resolves. In addition to treating
the foot, make sure the horse is being kept on clean and dry bedding.
Preventing thrush comes from proper management: clean the horse’s feet
thoroughly (several times a day) and keep his living conditions sanitary,
whether it is in a stall or in a paddock. No competent horseperson allows a
horse in his or her care to develop a severe case of thrush!
Lecture – The Equine Hoof
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Abscess
A hoof abscess is an infection in the soft tissues of the foot,
most commonly under the sole or hoof wall. Because the
soft tissues of the foot are encased in a rigid box (the hoof
wall and sole), the pus caused by an infection has no easy
avenue of escape. Pressure builds up, causing pain and
further disruption of the soft tissues. Because the pus tends
to move along the path of least resistance, most abscesses
break out at the coronary band.
Most abscesses start with a hoof crack or separation
(defect) of the wall and sole at the white line. This allows
dirt, mud, manure, tiny bits of gravel, and water to enter. As the horse puts weight on the foot,
this material packs deeper and deeper into the foot, causing disruption of the sensitive tissues.
Abscesses may also occur because of a bruise or wound to the sole.
Horses with a hoof abscess will often show sudden and
severe lameness, to the extent that they cannot put any
weight on the affected hoof. The hoof wall is often noticeably
hot to the touch over the abscessed area, and an increased
pulse in the arteries at the back of the fetlock is usually
evident. If you call out your farrier or veterinarian to examine
the horse, they may use a tool called hoof testers to squeeze
various areas of the hoof in order to identify sensitivity.
The most important part of treating an abscess is to identify
drainage. This is often accomplished by soaking the foot several
times daily in warm water and Epsom salts in order to encourage
the abscess to “pop” and drain. In severe cases, your veterinarian
or farrier may have to open up the sole or hoof wall to allow for
drainage. Once the abscess has started to drain, it is vital that the
area is kept clean and allowed to fully drain; abscesses can recur
if they do not heal properly the first time.
Lecture – The Equine Hoof
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Diagrams of the External Hoof
Frog
Bars
Hoof Wall
White Line
Sole
Collateral Groove/Sulci
Sulci of the Frog
Heel Bulbs
Lecture – The Equine Hoof
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Self-Knowledge Checks
1. Which of the following is not a skeletal
component within the hoof capsule?
a. Middle Phalanx b. Cannon Bone c. Distal Phalanx d. Distal Sesamoid
2. Which connective structures gives the leg the
ability to bend or flex?
a. Deep Digital Flexor Tendon b. Common Digital Extensor Tendon c. Superficial Digital Flexor Tendon d. Annular Ligament
3. Structures of the hoof that are exposed are
known as:
a. Insensitive b. Sensitive
4. Hoof wall growth begins at the:
a. Sole b. Periople c. Coronary Band d. White Line
6. The sole is designed to be the main weight-bearing
surface of the hoof a. True b. False
7. Which of the labeled structures below is the frog?
9. Which of the following situations would best assist
blood flow to and from the hoof?
a. Standing on shavings or sawdust b. Standing on a hard, concrete-like surface
10. A horse with a foul odor present at the frog most likely
has the beginning signs of:
a. An abscess b. Thrush c. Laminitis d. Boil
5. _____ are responsible for attaching the hoof
wall to the coffin bone as well as absorbing
shock and supporting weight
a. Hoof wall b. Periople c. Coronary Band d. Laminae
8. Which of the following is categorized as an internal
elastic structure of the hoof?
a. Bars b. Digital cushion c. Frog d. Heel bulbs
Lecture – The Equine Hoof
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Answers
1. Which of the following is not a skeletal component
within the hoof capsule?
b. Cannon bone
The three bones that are within the hoof capsule are P2, Distal sesamoid, and P3. The cannon bone is proximal to the hoof capsule
2. Which connective structures gives the leg the
ability to bend or flex?
a. Deep Digital Flexor Tendon
The Deep Digital Flexor Tendon (DDFT) attaches to the bottom of P3, allowing the leg to bend or flex
3. Structures of the hoof that are exposed are known as:
a. Insensitive
Structures of the hoof that are exposed (we can see) are known as the insensitive structures. These include the wall, bars, sole, frog, etc.
4. Hoof wall growth begins at the:
c. Coronary Band
The growth of the hoof wall begins at the coronary band
5. _____ are responsible for attaching the hoof wall to the
coffin bone as well as absorbing shock and supporting
weight
d. Laminae
Laminae are “leaf-like”, interlocking structures found on the innermost layer of the hoof wall. These structures attach the hoof wall to the coffin bone and help absorb shock, support weight, and expand the hoof
6. The sole is designed to be the main weight-
bearing surface of the hoof
b. False
The sole, which is the ground (bottom) surface of the hoof, protects the sensitive structures underneath it. The sole is not designed to be constantly bearing weight – if it does, it can become bruised
7. Which of the labeled structures below is the frog?
C
In the presented image, the structure labeled as “C” is the frog
8. Which of the following is categorized as an internal
elastic structure of the hoof?
b. Digital Cushion
The digital cushion is the main shock absorber of the hoof. This is an internal structure located behind the coffin bone
10. A horse with a foul odor present at the frog most likely
has the beginning signs of:
b. Thrush
Thrush is a bacterial infection of the hoof characterized by a foul odor, heat, and thick, black discharge from the grooves
9. Which of the following situations would best assist
blood flow to and from the hoof?
a. Standing on shavings or sawdust
Circulation of blood to and from the hoof is dependent on activity, hoof balance, and nutrition. A balanced hoof engages the solar surface – bedding such as shavings or sawdust will cup and engage the solar surface
Lecture – The Equine Hoof
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Glossary
Abscess – An infection in the soft tissues of the foot characterized by hoof inflammation and lameness
Bars – Found on the solar surface of the hoof, an extension of the hoof wall to add strength to the heels
Coffin Joint – The only synovial joint found in the hoof capsule
Collateral Groove – A depression found on each side of the frog as well as in the middle of the frog
Common Digital Extensor Tendon – Found on the front of the limb, attaches to the top of P3
and allows the limb to extend/straighten
Corium – Refers to the sensitive structures of the foot that contain the many nerve and blood vessels
Coronary Band – A rim of tough, vascular specialized skin that is responsible for hoof growth and nutrition
Deep Digital Flexor Tendon (DDFT) – Found on the back of the limb, attaches to the bottom of
P3 and allows the limb to flex/bend
Digital Cushion – An internal elastic structure that is the main shock absorbed of the hoof
Frog – A thick, wide, triangular-like structure found on the solar surface of the hoof
Heel Bulbs – Found on the back of the hoof to aid in shock absorption, can be easily bruised or injured
Hoof Capsule – Hard covering that protects inner sensitive structures, comprised of the
coronary band, periople, hoof wall, and solar surface
Hoof Testers – A diagnostic tool used to check for hoof sensitivity
Hoof Wall – A multilayered structure that grows from the coronary band
Horned Layer – Refers to insensitive structures of the foot
Laminae – Leaf-like interlocking structures that help attach the hoof wall to the coffin bone
Laminitis – Inflammation of the laminae
Lateral Cartilage – An internal elastic structure that provides resistance to the coffin bone when
taking weight
Periople – Found below the coronary band, provides a protective covering for new hoof wall
Solar Surface – The ground or bottom surface of the hoof
Sole – A thick plate of flaky horn that covers most of the solar surface to protect internal
sensitive structures
Thrush – A bacterial infection of the foot that is often the result of general neglect of the feet
Lecture – The Equine Hoof
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Trim – A practice performed by a farrier to remove excess hoof wall, frog, etc., should occur
routinely in order to maintain hoof balance
White Line – The junction between the wall and sole, seals off the sensitive structures of the
hoof from bacterial infiltration
White Line Disease – An ailment that results in the weakening of the white, often the result of
improper care of the hoof