Lower Limb Lesson
Has this happened to you? You've
got your horse in the crossties happily grooming him away and
some long time horse person ambles in, takes a look at your horse
and then says something completely foreign to you regarding your
horse. It could be something as simple as "looks like your
horse's knees are still open" to something more ominous
sounding as "your horse looks like he has bucked knees".
Immediately you freeze, possibly mumble something incoherent
and as they amble away and you think to yourself "what the
heck are they talking about"? You look at your horse's knees
and don't see anything resembling whatever term they used and
begin to get nervous. Should I ride him today? Is this something
serious? Who can I ask in the barn without feeling silly if the
answer is something simple. Well, we're here to help. Following
we'll try to give you a brief overview of some common terms heard
around the barn concerning horse's lower limbs. After reading
this article you may not know the terms down to the scientific
meaning and physiologic condition, but you'll at least know what
the heck they're talking about.
The lower limbs on a horse are such a complicated ordeal. There
are several bones, tendons, ligaments, joints, nerves, blood
vesselsthe list goes on an on. The pictures depicted should give
you a basic understanding of the anatomy of the equine lower
limbs. Refer to these pictures when we describe the following
Figures 1 & 2).
When you look at a horse's foot you need to evaluate not only
the foot but how the foot attaches to the pastern. Usually you
do this by measuring angles. Most of you have seen your farrier
grab his little foot protractor and slap it onto your horse's
foot, read the measurement, then either finish up with the foot
or do a bit more work on the foot. Well, normal foot angles are
generally 45-50° in the front and 50-55° in the rear.
Now every horse doesn't read the literature mind you and some
are different but normal for that horse. But measuring that axis
can give you a better understanding of your horse's feet, and
leads us to learning the first of our "heard terms".
Club Foot is a foot that has a foot axis of 60° or
more. If it is just in one foot it usually is due to a previous
injury that has prevented the horse from using the foot for an
extended period of time. When both feet are affected, it could
be genetic or due to some type of nutritional deficiency during
growth. It's caused by contracture of the deep digital flexor
tendon (if you look at the limb pictures you can see that it
attaches down onto the coffin bone within the hoof) which pulls
on the coffin bone. Bull-Nosed Foot is a foot that has
been rasped down in front to fit a shoe (see Figure 3). Buttress Foot has
swelling in the front of the foot directly above the coronary
Figure 4). This can be caused by ringbone or a small
fracture of the very front of the coffin bone. Ringbone
is new bone growth occurring at either the proximal (P1), middle
(P2) or distal phalanx (P3). High ringbone is between P1 and
P2, whereas low ringbone is between P2 and P3. This bone production
is usually initiated by inflammation in the covering of the bone,
then bone production is started and grows over the normal bone.
It is not a favorable prognosis, especially if it involves the
joints, since treatment is limited once the ringbone is present.
Then when you evaluate the foot further you should see how they
relate to one another and to the entire leg itself. Horses can
be toed out or toed in which are pretty self explanatory.
Toed out horses point their toes out slightly and are sometimes
called splay footed. Toed in horses point their toes in
slightly and are often called pigeon toed. Horses are
also base wide or base narrow which means that
the space between their feet is either wider or narrower than
the space in between their front limbs directly under their chest.
So stand your horse like you would for a halter class (all four
legs next to each other and squared up) and evaluate your horse's
front legs. Knowing this type of information will help you better
understand your horse's movement. A base-narrow, toe in conformation
Figure 5) often paddles which means their foot
moves out during its flight. This paddling often results in excessive
strain to the outside of the leg causing windpuffs (discussed
later) or sometimes ringbone. The outside of the foot will wear
down quicker as well. Base narrow, toed out conformation (see Figure
6) horses often wing, which means their foot's
flight goes inward often hitting the other forelimb. Plaiting
can also occur in these horses when the front feet land directly
in front of the each other which can cause stumbling. This plaiting
often results in injuries to the inside of the cannon and splints
(discussed later). A base-wide, toe out conformation horse (see Figure
7) also wings to the inside landing on the inside hoof
wall with similar injuries to the base narrow, toed out horses.
Splint bones are the small bones to the inside and outside
of the cannon bone (see
Figures 1 & 2). These bones are attached to the cannon
bone by ligaments and therefore support or "splint"
the cannon bone. These bones when injured or inflamed can cause
localized swelling over the site and cause pain and lameness
for the horse. Splints often occur to the inside splint
bone when injured by the opposite leg, as we discussed in toed
in horses. Popping a splint is a term often used when
the horse initially injures the splint bone and it is sore and
inflamed. Cold splint or old splint is often used
after the inflammation and pain has subsided and there is simply
a non painful bump on the leg with no associated lameness.
Moving our way up we come to the knees. There are offset
or bench knees (see Figure 9) where the cannon bone
is offset laterally (or to the outside of the body) below the
knee. In these horses the inside splint bone is under a lot of
strain and splints there are common. There are bucked knees
(also known as knees sprung, goat knees, over
in the knees) (see
Figure 10) where the knee is constantly a bit forward
like the horse is getting ready to jump. There are knock knees
Figure 11) where the knees are displaced to the middle
causing more tension to the inside of the legs and there are
bow legged horses (bandy-legs, varus) (see Figure
12a & 12b) where the knees are displaced to the outside
causing more tension to the outside of the legs. There are calf
kneed (or sheep kneed) (see Figure 13) horses where the knees
are offset back and look like they're trying to bend the wrong
way. This is a weak conformation and the limbs can seldom remain
sound with lots of work. There are open knees (see Figure 14) in young horses that
are still growing. There is an irregular profile to the knee
joints in these horses that cause a flaring out in the bone and
hair. This indicates further growth in height and heavy work
or repetitive work should be limited until it is gone. Then there
are closed knees which shows that the horse has no more
growth potential in that area and this can be verified with radiographs
of the area.
Moving up in the rear limbs we hear terms concerning the hocks.
Cow hocked (see
Figure 15) horses have a base wide conformation from
the hocks down, meaning the hocks are closer together and point
towards each other and the feet are wider apart. This causes
a lot of strain to the inside of the hock joint. Sickle hocked
(or curby conformation) (see Figure 16) horses stand under their
body from the hock down resulting on increased strain to the
back of the hock. This is called curby conformation because it
predisposed horses to curbs which is inflammation to the
plantar ligament (right below the point of the hock in the back)
causing swelling, inflammation and pain. The rear limbs can also
be bow legged as we discussed earlier with the knees (see Figure 12b).
In both the front and rear limbs we can see windpuffs
which is a swelling around the fetlock caused by increased joint
fluid due to an unknown reason. Sometimes the swelling is small
and not very noticeable and sometimes it is very large and resembles
a cluster of grapes. Windpuffs are more common in the rear limbs
and are often seen in horses with straight fetlocks. Another
term along that same line is bog spavin which is the same
problem at the hock joint. There is increased joint fluid resulting
in swellings to three places around the hock. Bog spavin is most
common in horses with straight hocks, or that are sickle hocked
or cow hocked. Both windpuffs and bog spavin are NEVER associated
with heat, tenderness, lameness or radiographic changes-in short,
they're more of a visual disturbance than anything else.
I hope these terms and pictures help you out with all the comments
you can hear amongst horse owners. I know we touched on quite
a few, but it will give you a better overview and a starting
place if you would like to learn more on a certain condition
or conformation. And now the next time someone you don't know
saunters up to your horse and makes a comment such as "it
looks like your horse's knees are still open" you can quickly
comment back to him "Why yes they are, he is only 2 years
old and has a bit more growing to do. I'm taking care to not
do a lot of repetitive motion or heavy work with him and concentrating
more on ground work until I get the radiographic confirmation
from my veterinarian that they've closed all the way." WOW!!
A little vocabulary goes a long way.
West Nile Update
We have been trying to keep you up to date on any new information
out there on West Nile Virus. From what we are getting from area
veterinary teaching hospitals the general consensus of vaccine
administration has suggested to repeat a West Nile vaccination
60-90 days after the annual dose in 2003. They are worried about
the virus being aggressive this year with this year's high threat
of mosquitoes. All the cases that we attended to last year were
in August or after, so it may prove to be a good idea to rebooster
your horse in mid July as they are suggesting. This should give
their immune system one last kick prior to the worst insult.
If you would like further information please do not hesitate
to call or email us. We've started a list of people interested
in reboosters and will try to schedule them as appropriately
Did You Know?
The minimum period of time for a mosquito to mature from an egg
to an adult is 9 days. Therefore, changing water tanks or any
other standing water at least once a week would be an effective
way to prevent the lifecycle of a mosquito.
Bugs and Bumps
The bug season is upon us once again. Not only can those pesky
mosquitoes carry potentially fatal diseases (West Nile, Eastern
and Western Encephalitis), but they and other biting insects
can also send some of our poor beloved horses into hives. Some
can be horribly itchy, some can make the horse appear to have
millions of tiny bumps all over their body, some can be as big
as a half a watermelon (we called that guy Lumpy Lou)-in other
words, each case is slightly different. The actual term for this
is "urticaria" but most people just call them hives.
Urticaria can be caused by insect bites but don't think that
each hive is one individual insect bite. Just a few bites can
cause them to break out in widespread hives. Likewise, insect
bites are not the only thing that can cause your horse to get
hives. Hives can also be caused by certain medications, vaccinations,
feeds, chemicals such as insecticides, stress, infections, etc
so sometimes it is hard to identify the actual source of the
problem. But for those horses in the appropriate time of the
year that have had no changes in feed, environment, sprays, stress
or are on any medications-insects are often to blame.
The clinical signs of urticaria often occur suddenly but may
occur over a longer period of time. Wheals or "plaques"
form on the skin often within a few minutes to hours of exposure
to the inciting agent. The wheals are elevated, rounded, flat-topped
lesions on the skin that can range from 1/2 an inch to 5 inches
in diameter and may possibly be depressed in the very center.
Sometimes the wheals can also leak serum and appear that they
have "burst" open. The wheals can occur anywhere on
the horse including the back, flanks, neck, eyelids and limbs.
Severe reactions may be preceded by a fever, period of inappetance
or dullness. The horse may also show signs of excitation or restlessness.
The areas may or may not be itchy to the horse. A localized edema
or "puffiness" may also accompany the wheals.
Horses often spontaneously recover from urticaria without any
specific treatment. That's why in uncomplicated cases I tell
the owner we are going to treat the horse with aggressive benign
neglect (wink, wink). If any specific treatment, oral or topical
medication, or different feed was administered within a few hours
of the reaction, they should be discontinued. In rare instances,
a veterinarian may need to be contacted in severe, life-threatening
hypersensitivity allergic reactions. Prevention usually centers
on limiting the horse's access to the allergic substance. It
may be quite easy to decide what caused the allergic reaction
(you just used a new fly spray) or it may be difficult. It may
help to keep a log book of treatments, applications, exercise
regiments, etc of a susceptible horse in order to localize the
specific cause of the urticaria.
In the case of insect bites, you should attempt to limit exposure
to biting insects. (I know, I know...easier said than done.)
Water based fly spray, low running fans, fly spray dispensers
in the stalls, fly sheets, diligent cleaning in stalls, etc are
all helpful in this task. Beware of oil based fly sprays, I have
seen several horses that break out in hives from application
and then it is very difficult to wash off since it is oil based.
They do last longer, just test it out in a small area first BEFORE
application. There are also treatments such as antihistamines
that can help prevent the body from responding so over zealously
to the insect bites. However, antihistamines do need to be used
cautiously in show horses due to drug testing. In more severe
cases, anti-inflammatories or low dose steroids can be used if
needed. Also, in refractory cases where usual therapy is not
testing is now available. Bloodwork can be obtained from your
horse and sent to a laboratory that will send you a report back
with what your horse is allergic to. They can screen environment,
biting insects, feeds, etc and the positive hits can be
combined into "allergy shots" for your horse to desensitize
So everyone, take a deep breath, grab those fly swatters and
come out swinging. If you have any questions concerning equine
urticaria, feel free to contact us via phone or email.
Greener Pastures Veterinary Clinic, Inc. is pleased to announce
all the new arrivals to our care. Let's pass out the carrots
(you know, instead of cigars) and celebrate.
Mares that had fillies: Some Kinda Dunny owned by Jose
Vazquez on 1-20, Steady Tradition owned by Jose Vazquez on 2-8,
Kanie owned by Chris Konior on 3-9, Schatze owned by Deidre LaMontana
on 3-9, Twilla Tweed owned by Shari Williams on 3-12, Streakin
Marita owned by BR Barrel Horses on 3-16, Hope owned by Carousel
Program on 3-26, Allie owned by Darlene Mannix on 4-10, Hailey
owned by Deb Halsted on 4-14, Sweetheart owned by Jackie Thomas
on 4-15, Nikki owned by Dee Knight on 4-21, Stinky owned by M.
King & J. Fuller on 4-23, Chevelle owned by Kenny Honkisz
on 4-25, Missy owned by Pam Finley on 4-27, Roxy owned by Wisdom
Ranch on 5-3, Sis owned by Pam Gasche on 5-15, Fantasia owned
by Kris Benner on 5-23, Spring owned by Wisdom Ranch on 5-24.
Mares that had colts: Fifi owned by Kris Benner on 1-25,
Bright Linx owned by Jose Vazquez on 3-2, Bug owned by Hodson
Farm on 3-9, Kelly owned by Blue Ice Minis on 3-17, CC owned
by Glenn/Kathy Martin on 3-17, Vinnie owned by Joan Chismundy
on 3-25, Beauty owned by Jackie Thomas on 4-10, Rose owned by
Shari Williams on 4-14, Bonnie owned by Gail Marzotto on 4-18,
Ginger owned by Cathy/David Wiegele on 4-22, Tequilla owned by
Kenny Honkisz on 5-1, Dara owned by Janet/Rex Veach on 5-16.