Thal Equine, LLC
(505) 438-6590 ● drthal@thalequine.com
www.thalequine.com
69 Bonanza Creek Road, Santa Fe, NM 87508
Understanding Lameness: A Lecture
for Horse Owners - Synopsis
By Doug Thal, DVM
The purpose of the lecture was to make horse owners more aware of lameness and its
diagnosis, so that they may become better stewards of their horses and get more
enjoyment from them.
Why is lameness such an important topic?
 Lameness accounts for the greatest losses for the equine industry. Hundreds of
millions of dollars annually – more than twice the losses experienced from colicare the result of lameness.
 Lameness affects individual horses at all levels, from subtle reduced performance
to complete loss of use or euthanasia.
 Lameness accounts for great pain and suffering for horses of all breeds and
disciplines. Sadly, many horses are asked to perform when they are in pain
because of owner failure to recognize lameness.
What causes lameness?
Lameness results from pain coming from any component of the limb which contains
nerve endings. Wounds to skin, connective tissue bruising, muscle pain, arthritis (joint
inflammation) , tendon sheath and bursal inflammation, tendon and ligament injury, and
injuries to bone; all can cause lameness.
Forelimb versus hind limb lameness. A high percentage of forelimb lameness is below
the level of the fetlock. Upper limb lameness is not common in adult horses. It is more
common in younger horses because developmental orthopedic disease (osteochondrosis,
epiphysitis) is quite common in the upper limb in young horses.
Forelimb lameness is generally easier to diagnose than hind limb lameness. Lameness is
easier for most people to recognize in the front limbs than in the hind limbs. The massive
musculature of the upper hind limb makes diagnosis and imaging much more difficult.
Dr. Thal went on to briefly demonstrate some anatomic landmarks that every horse
owner should know. On the front limb, he pointed out withers, scapula, shoulder joint,
humerus (upper arm) elbow joint, carpal joints, fetlock, pastern and coffin joints, and the
flexor tendons.
On the hind limb, he pointed out lumbosacral joint, point of hip, location of hip joint,
stifle, hock, cannon, flexor tendons, fetlock, pastern, coffin joint.
Horse owners should be able to point to these locations on their horses.
He then touched on the evolution of the horse’s limb and locomotion. The big points
were:
 Horses walk on a “modified single finger or toe,” but evolved from multi-toed
predecessors.
 Intense selective pressure for being able to evade predators resulted in lightening
and lengthening of the lower limb and bulking up of the upper limb “motor” to
create an animal that had explosive speed.
 A 55 million year old horse, Hyracotherium, was dog-sized, and had a paw which
looked like a dog’s.
 Remnants of this evolutionary process can still be seen in the anatomy of the
modern horse. The splint bones are remnants of the time when horses walked on
multiple toes. Remnants of foot pads are the chestnuts (above the carpus and hock
on the inside of the limb) and ergots (located at the back of the fetlock).
 The point of the hock is the equivalent to the human heel. The carpus is the
equivalent of the human wrist.
Dr. Thal then briefly discussed conformation as it relates to function and thus to
lameness. The sole purpose for this was to establish the connection between
conformation and lameness. The point is that horses with poor conformation are more
likely to experience problems with joints, tendons and ligaments than are horses of
“normal” conformation. Examples given were angular limbs (pigeon toes, for example)
causing a horse to paddle when it moves and setting it up for uneven mechanical forces in
the limb which over time leads to damage of joints and arthritis.
Understanding lameness basics (and working with an equine veterinarian with experience
in lameness) allows a horse person to:
 Purchase horses who do not have current lameness and are conformationally less
likely to become lame, via the Pre-Purchase Exam.
 Recognize conformational predispositions in their horses and manage for
treatment and prevention.
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Recognize or at least suspect when lameness is the root cause of your horse’s
poor performance, versus training issues, and get the lameness problems
diagnosed and treated.
Breed better horses. Understanding lameness and basic form and function allows
breeders to breed horses that are conformationally superior and thus less likely to
become lame.
The next part of the lecture described the lameness exam as it is performed by an
equine veterinarian. There were several take home points.
The lameness exam is a detailed veterinary exam taking into account the horse’s history
including signalment (breed, age, use, etc.), a standing exam, exam in movement, flexion
exams, diagnostic anesthesia( nerve blocks) and imaging (examples are x-ray, ultrasound,
MRI). The lameness exam is as much an art as it is a science, as some of the above tests
are very subjective. The exam synthesizes all of the above to come to a conclusion and
find a treatment. The exam relies on an understanding of anatomy as its basis, and
requires experience and a methodical approach to perform well.
Lameness diagnosis and treatment has
been studied for hundreds of years. Dr.
Thal displayed slides of drawings that he
had of equine limb anatomy from a book
written in 1894. These drawings show a
surprisingly good understanding of the
mechanics of the limb. There are many
treatments developed then which are still
used today.
The lecture then turned to the components
of the lameness exam.
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The first part of a thorough lameness evaluation is a thorough history. Examples
of information gathered is signalment (breed, age, use), the date that lameness
was first noticed, how the injury occurred if it is known. All of these are
important questions which veterinarians ask
and horse owners should be try to provide
accurate answers to.
Examination is done first at a distance to
evaluate conformation and demeanor.
Following that, more careful examination
and palpation of specific structures for
swelling, heat, pain, etc, is performed.
The next part of the exam is to see the horse
in movement. Lameness is mostly
evaluated at the trot. Most thorough lameness exams are performed on firm to
hard, even footing. Examination often includes circles to both directions and may
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include inclines or specific patterns. For the diagnosis of some types of lameness
problems, having a rider up can be advantageous.
Flexion exams are performed
next. This involves putting
specific joints or regions of the
limb under stress for a specified
time. The horse’s degree of
lameness is assessed when it
trots off after the flexion relative
to that before flexion. This is
another screening test to help localize
lameness to a specific area. As with many parts of the
exam, flexion tests must be interpreted in light of what is
normal for that specific horse.
Hoof testers allow pressure to be placed upon specific
regions of the foot, in search of a pain response. The key
to smart interpretation of hoof tester and flexion exams is
knowledge of normal responses, which can only be
gained through a methodical approach and lots of
experience.
All of the above parts of the exam are essentially pieces of a
puzzle taking form.
At this point in the exam, we have an understanding of which limb is the lame one,
and we may or may not have a hunch as to where in the limb the problem is. If the
examiner is not certain of where the problem is:
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Nerve blocks are used to methodically numb portions of the limb. A “block” is
injection of a local anesthetic agent around specific nerves or into specific joints
or other synovial structures. The horse is assessed before the block, the area in
question is numbed, and the horse is asked again to trot off. Either there is
improvement in the lameness or not. If there is not, the process is continued on
specific nerves progressing up the limb until the lameness is lessened or
abolished. Specific joints and tendon sheaths can be blocked for a more specific
localization of lameness. Blocks into a joint or tendon sheath require surgical
cleanliness to prevent infection of these structures.
Once we have found the region from which the pain is coming from,
we use diagnostic imaging to describe the structures in that area.
Imaging includes x-ray (radiology) to image bone, ultrasound to
image soft tissues, and may include less common modalities like
MRI, CAT Scan, and Nuclear scintigraphy.
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X-ray is the first line of imaging for bone. It is less useful for
soft tissues. X-ray is often performed in the field with
portable equipment. More difficult studies are often
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performed in the clinic. Digital x-ray is new technology
which does not rely on film. It is quickly becoming the
standard for equine x-ray.
Ultrasound is excellent for imaging soft tissues, but
cannot penetrate healthy bone. It is used commonly to
image tendon, ligament, the surface of bone, and other
soft tissues. An example slide showed imaging of a
healthy suspensory ligament branch versus an injured one.
All of the above, done and interpreted correctly, provides a correct diagnosis.
History
Obvious problem
Exam at Rest
Exam movement
Flexion exam
Treatment
Hoof testers
Nerve blocks
X-ray
Ultrasound
Other imaging
Conclusion
DiAGNOSIS
MRI
No diagnosis
Other diagnostics
Correct and complete diagnosis leads to correct and complete treatment. Examples
of treatments were then given just to illustrate the point that until we have a diagnosis
there is no way to know what the treatment and prognosis will be.
A case study was presented to illustrate the points that had been made about lameness
and the lameness exam.
The case was a 5 year old quarter horse gelding who has a history of stepping in a hole
on a trail ride 2 weeks previous and becoming suddenly lame on the right front limb.
The owner treated the problem himself for a few days, leaving the horse out in the
pasture and giving bute daily for a few days. The lameness improved while on bute, but
worsened immediately when it was discontinued. He finally decided to call the vet when
the “bute just didn’t seem to be helping fix the problem.”
On exam, the right front pastern area is slightly swollen. In movement the horse is 3+/5
lame at the trot, worse to the inside circle. Flexion of the digit causes a strong 4+/5
response. Hoof testers are negative. The palmar digital nerves are blocked low in the heel
and the horse is 50% improved. A block is performed above the swollen area on the
inside of the pastern. This involved blocking the medial palmar digital nerve at the level
of the base of the fetlock. The horse became 100% sound following the block. The area
was then imaged. X-rays showed no problems. Ultrasound was then performed and
showed a tear in the medial collateral ligament of the pastern joint. We now have a
specific diagnosis- tear of the medial collateral ligament of the pastern joint and
associated joint inflammation.
Treatment in this case involved forced rest, injection into the pastern joint, pulsed
shockwave therapy for the torn ligament, and anti-inflammatory drugs. The prognosis is
guarded to fair given the nature of the injury. Low grade chronic arthritis of the pastern
joint is common after this injury. The prognosis would have been much better if the horse
could have been treated earlier.
Dr. Thal then went on to discuss the future of lameness diagnosis in horses.
MRI is being used more commonly in equine lameness diagnosis and is changing our
understanding of lameness in the foot. MRI allows both soft tissue and bone to be
examined in never-before-seen detail. An example of where this is making a difference is
in our understanding of problems in the back half of the foot. We are finding that what
we thought was simple pain in the navicular area can actually be broken down into many
specific conditions, examples of which are:
 Tears of the deep digital flexor tendon low in the foot
 Primary inflammation of the navicular bursa
 Primary navicular bone degeneration
 Injury to navicular supporting ligaments.
Each of these is a separate problem (although they may occur together) and each carries
with it a specific treatment program and prognosis. The detailed information coming
from MRI can allow more targeted treatment and a better understanding of the prognosis
for return to use.
In conclusion, Dr. Thal made several points:
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Horse owners should establish a relationship with their equine veterinarian and
use him or her to help clarify lameness questions.
Always call sooner on a suspected lameness problem rather than waiting.
Be careful of inaccurate lameness information on the internet. Use your equine
vet to help screen this information for you.
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Be careful of the supplement game. There are hundreds of products out there that
make a variety of claims for solving lameness problems. These products are
expensive and in many cases are completely ineffective or certainly have no proof
of effectiveness. Some of these products don’t even contain the ingredients they
claim to contain. There is no regulation on these products and so it is up to the
consumer to beware. In Dr. Thal’s opinion, money is generally better spent on a
lameness exam and the search for a correct diagnosis.
New technology like MRI will add knowledge to the field but is no substitute for
a good exam. A thorough, methodical exam will always be the cornerstone of
lameness diagnosis. Be prepared to haul your horse for the diagnosis of complex
lameness problems. For many reasons, these exams are better performed in a
clinic setting.
For more information, feel free to contact us at:
info@thalequine.com