THE EQUINE FOOT: THE RELATIONSHIP BETWEEN DISEASE,
CLINICAL SIGNS, DIAGNOSIS AND TREATMENT.
Andrew H. Parks, MA, Vet MB, MRCVS, Diplomate ACVS
College of Veterinary Medicine
University of Georgia, Athens Georgia
Reprinted with permission from the North
American Veterinary Conference.
Original printed in the 2001 NAVC conference proceedings
|DIAGNOSIS AND CLINICAL SIGNS
The presenting symptom is one manifestation of abnormal form
or function, usually lameness or abnormal appearance. This
initial symptom directs the course of clinical investigation
for more subtle symptoms to better define the disease process
to obtain the most accurate diagnosis possible. The presenting
symptom may obviously identify the horse's foot as the site of
disease, However, the source of the problem is not obvious in
many horses with lameness originating from the foot. Therefore
the breadth of the examination may be determined by the
specificity or vagueness of the presenting symptom(s).
The basic principles or physical examination of the foot
follow those for the rest of the musculoskeletal system
whenever possible: visual observation, palpation for pain and
heat, flexion and extension. Emphasis is given to identifying
the cardinal signs of acute or chronic inflammation - the
commonest causes of disease in the musculoskeletal system.
Again, it is the structure of the integument of the foot that
makes it different from the rest of the limb. The hoof offers
clues that are not present elsewhere , yet the rigid hoof
capsule inhibits basic palpation of the structures within the
foot. Therefore it is important to develop an ability to
"read" the hoof capsule (which seems to be a life long
process). Visual examination of the hoof capsule in
conjunction with the phalangeal axis from the lateral, medial,
dorsal, palmar and solar aspects to compare the balance and
conformation of the distal limb with an "ideal balance and
conformation" is straightforward. Closer observation reveals
more subtle signs. Examination of the coronary band should
show any local areas of proximal or distal displacement.
Examination of the growth rings below the coronary band should
show local variations in the spacing of the growth rings. By
sweeping ones hand on the outside of the hoof from the
coronary band to the weightbearing surface, convexities or
concavities in a proximal to distal direction can be
identified. Similarly, by sweeping an outstretched hand around
the hoof from the medial to lateral heel, deviations from the
normal smooth curvature can be identified as increased or
decreased convexity and even local concavity can be
identified. Palpation of the coronary band in a similar manner
may reveal lipping when the coronary band extends abaxial to
the wall. Taking any one of these more subtle symptoms alone
can be misleading, but taken together they can provide
supporting evidence. For example, local coronary band
displaced proximally at the junction of the toe and the
quarter may be accompanied by growth rings that are closer
together and an exaggerated convexity in the hoof capsule at
that point in the horizontal plane. Taken together, these
findings are very suggestive that there is excessive
compressive vertical stresses within the hoof wall at that
point. But if the coronary band is displaced without the
difference in spacing of the growth rings or convexity, more
caution is needed before this assertion can be made.
Having examined the outside of the foot, is important to
maximize the information we can learn about the inside of the
foot. Heat within the foot can often be readily appreciated.
However, because pain within the hoof is rarely appreciable on
digital palpation, compression of the hoof with hoof testers
or percussion with a hammer is necessary to localize pain.
Cleaning the weightbearing surface of the foot by lightly
removing the surface layer of the sole, frog and distal wall
indicates any potential entry sides for infection, usually
seen as small dirt filled cavities. Also visible may be
speckled red discoloration of the horn indicating hemorrhage
into the hoof capsule from underlying trauma. Interestingly,
hemorrhage within the hoof maintains its blood red color
rather than turning black and blue as bruises do elsewhere.
Hemorrhage within the wall represents a past event and not
necessarily an ongoing process, though of course, it may still
Various ancillary diagnostic aids are used to gain further
information about the disease process: exploration, regional
and intra-articular anesthesia, radiography, ultrasound,
nuclear scintigraphy and thermography.
Removal of exfoliating hoof and careful exploration of tracts
is indicated if infection is suspected.
Local anesthesia is very useful to localize lameness to the
distal limb. Unfortunately, comparing the results of the
different perineural blocks and intrasynovial anesthesia has
not proven to be as useful a discriminator in determining the
affected tissues as clinicians would like it to be. Recent
advances in our knowledge of the affects of these techniques
have, if anything, introduced ambiguities in interpreting the
results obtained with local anesthesia.
Radiography is a time honored technique that has proven useful
in identifying osseous disease, though ambiguity persists in
interpretation of specific findings, for example navicular
disease or pedal osteitis. Only recently has the examination
of the soft tissues received more attention, both in their own
right and in the relation between the soft tissues and the
osseous structures. Some diseases of the foot require
radiographs to make a diagnosis, in other diseases radiographs
are a useful adjunct to confirm a diagnosis or help determine
the severity of a disease process, while in other diseases,
radiographs are of limited benefit except in ruling out other
Ultrasound is a well established modality for examination of
soft tissue structures of the limb, but it is only recently
that it has been used for structures within the foot, either
by examining the deeper structures from above the coronary
band or through the frog. Further development can be expected
in this area.
Nuclear scintigraphy has proven to be a valuable aid in
guiding the interpretation of equivocal radiographic changes,
identifying pathological processes before radiographic changes
are evident and in identifying some processes for which
radiographic changes cannot be visualized.
Thermography has been less enthusiastically embraced that
ultrasound and nuclear scintigraphy because interpretation of
the results at this juncture is more ambiguous. But it is a
technique that deserves more attention, at least until its
interpretation has been fine tuned enough so that more precise
benefits of the technique can be identified.
In summary, examination of the equine foot offers many
challenges. While there are a finite number of tissues within
the foot and a limited number of pathological processes that
can affect these tissues, this knowledge does us no good
unless we can put the two together. With the advent of
ultrasound and scintigraphy, we can now make diagnoses that
were impossible 20 years ago; for example, insertional
tenopathy of the deep digital flexor tendon. With the
development and application of newer technology, the obvious
examples being computed tomography and magnetic resonance
imaging, we will be able to make diagnoses in the future that
are currently impossible; for example, sprains of the many
small ligaments within the foot.
Just as the foot shares many disease processes and symptoms
with the musculoskeletal system, so it shares treatments.
Hence the focus of the ensuing discussion will focus on
principles of general musculoskeletal diseases and specific
treatments limited to diseases of the foot.
Treatment may be directed at a symptom(s), a pathogenic
process, or a specific diagnosis. Symptomatic treatment is
likely to have the broadest applicability, but may not address
the cause. Treatment based on the type of pathogenic process
is more likely to be effective against the cause but requires
more specific diagnostic information to implement. Treatment
directed at a specific disease, i.e. a specific pathogenic
process in a specific tissue is obviously optimal, but a
specific treatment may be unknown, or a specific treatment may
exist that appears to be effective empirically without a
rational basis for its use. Only treatment that can be
discussed in generalities is covered below.
Treatment based on symptoms
Rest is employed to prevent exacerbation of a disease or
injury, and allow tissues to heal.
Pain is frequently the most prominent symptom. Pain is
obviously controlled for humanitarian reasons. Pain is also
controlled to improve function, either to make the horse sound
enough for a specific purpose, or to prevent complications
secondary to prolonged excessive weightbearing by unaffected
limbs. Pain may be controlled or reduced by pharmacological
means or by biomechanical manipulation of the distal limb.
Phenylbutazone is by far the most commonly used analgesic, but
other non-steroidal anti-inflammatory drugs and DMSO are used
especially when systemic endotoxemia is also suspected as part
of the underlying pathogenesis of the disease.
Correcting poor balance may correct some causes of lameness.
For other diseases restoring normal balance may minimize
discomfort and/or slow progression. For example, trimming and
shoeing may reduce the moment about the distal interphalangeal
joint, which decreases the stress in structures involved in
flexing this joint during weightbearing and breakover.
However, be cautious about changing the balance in sound
horses! While poor conformation cannot be readily corrected,
it may be compensated for by shoeing and trimming, though this
often involves a compromise.
Providing stability may be necessary for several reasons:
within the hoof capsule itself, either following a crack or
avulsion; between the hoof capsule and the distal phalanx in
laminitis; or between the skeletal elements themselves. As
well as providing an optimal environment for healing,
stabilizing the digit often provides pain relief. There are
frequently several options, the choice of which will depend on
the severity of the instability. Hoof defects or cracks may
require bridging, reconstructing or casting. Instability
between the hoof capsule and the distal phalanx in laminitic
horses usually involves shoeing to minimize further rotational
forces. Instability about the distal interphalangeal joint in
either the dorsopalmar plane, e.g. post deep digital flexor
tendon rupture, or the mediolateral plane, e.g. post trauma to
the collateral ligament may be shod to decrease distracting or
rotational forces, or cast.
As wounds heal of the hoof heal in very much the same manner
as elsewhere on the body, the basic principles should be
followed just as rigorously. The proximity of the foot to the
ground predisposes the foot to contamination and further
injury, and the role of the hoof in weightbearing may
necessitate additional precautions. Injuries to the hoof can
seldom be closed by primary intention except those limited to
the coronary band.
Treatment based on the pathological process
Infection may involve any of the structures of the foot. All
benefit from either drainage, debridement or lavage. Tetanus
prophylaxis is mandatory. Superficial infection of the
epidermis is generally treated by debridement and exposure to
air. Supplemental treatment with topical antibiotics or
astringents is likely to decrease the recurrence for some of
these diseases. All of them benefit from protection from
excessive moisture and fecal contamination.
Dermal and subdermal infection proximal to the coronary band
is treated as it is elsewhere on the limb. Below the coronary
band exposure of infected structures involves a compromise
between providing adequate drainage and maintaining stability
of the hoof capsule. Broad spectrum antibiotics are routinely
used for deep digital infections and are frequently
supplemented by regional intravascular infusion and topically
Neoplasia is not common enough to make general recommendations
except to say that keratomas require excision.
Ischemia is involved in the pathogenesis of laminitis and
suspected in the pathogenesis of navicular disease. Typically
it is treated with vasodilators, rheologic agents and
The treatment of degerative processes within the joints and
bursa are well documented elsewhere, but involve pain control,
joint lubrication and chondroprotection with various systemic
and intra-articular medications.
The symptomatic mainstays of traumatic injuries are rest,
analgesia and anti-inflammatory drugs. If the injury is the
result of repetitive trauma, the cause must be removed or
recurrence is inevitable. This may involve improving balance,
providing protection or the changing nature of athletic
activity or the exercise surface. Most fractures of the distal
phalanx and navicular bone are treated conservatively by
minimizing distracting forces. Occasionally, fragment removal
or internal fixation is required.