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2003 Spring 

 

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 terms (See 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 band (see 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 horse (see 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 (valgus) (see 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 as possible.


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 entire body
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 working allergy
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 him.

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.


Birth Announcements

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.