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Spring 2006 

 

A Joint Effort

Think of it from the mechanical point of view. Horses are large animals with the majority of their weight and carriage being carried by four small limbs. Let’s break it down even further with a specific example: consider a jumper, one thousand plus pounds of flesh and bone plus the inertia of a large moving object landing on two limbs a few inches in diameter after each jump. We sure ask a lot of our performance horses, sometimes both physically and mentally. However, we need to make it “a joint effort” to make sure our horses stay as comfortable as possible while they are working hard to please us.

Figure 1

Let’s first consider the joint itself (see Figure 1). The type of joint we are going to focus on in this article is a synovial joint. Synovial joints are the “ball bearings” of the horse. A synovial joint consists of two bone ends that are covered with cartilage. Cartilage within the joint is the smooth, resilient material that allows the bone to slide back and forth and move fluidly. The joint is held in place by a joint capsule, a fibrous material that surrounds the joint and is attached to the bones and the collateral ligaments (ligaments on the sides of the joint that help hold it in place as well). There are also cruciate ligaments that cross within some of the joints that likewise hold the joint steady. Now, looking inside the joint capsule there is a synovial membrane that produces synovial fluid (joint fluid) that lubricates the joint and again helps with fluid motion. All of this “architecture” so to speak is made with one thing in mind… to keep the joint in the correct position and lubricated to keep everything moving smoothly.

A healthy joint is maintained in several different ways. Often times owners focus on the medicinal aspects of it as their only “weapon” against the evils of degenerative joint disease (DJD). But I want to make sure you realize how important basic husbandry can be with maintaining healthy joints. Likewise, you need to be aware of the importance of appropriate exercise, breed selection and training when you consider the joint health of your horse. We will discuss further the disease process of DJD itself later as well and will touch on some medical aspects of therapy… but I cannot stress enough the importance of BASIC HUSBANDRY NEEDS of a horse. Did I mention how important BASIC HUSBANDRY can be in joint health? I did? Okay… I’ll continue.

Let’s first step back and actually look at the horse in question first. We should consider poor conformation, i.e. not born with the “perfect” legs, when considering utilizing a horse for different disciplines. Maybe the proverbial “perfect legged” horse doesn’t even exist, but there are some obvious deviations from perfection that can be quickly diagnosed. We have previously discussed the ramifications of crooked legs, bow legs, cow hocked horses, pigeon toed front limbs, horses forward at the knees, etc. (Spring 2003 Newsletter, Lower Limb Lesson). In a normal horse, a line through the center of the limb should perfectly bisect it (see Figure 2).

Figure 2

With imperfect conformation, it all comes down to the fact that the massive weight of your horse is not being distributed evenly down the limb, within the joint space and through the soft cushion that helps support the joint. For example, a pigeon toed horse has fetlocks that are turned out slightly, resulting in more weight and stress to the inside of the joint. This will result in an increase of “wear and tear” on the inside of the joint and a hastening of arthritis to develop in this area. I was once called out to do a prepurchase examination on a middle aged, overweight, barely 15 hand quarter horse gelding. I was talking with the potential purchaser and asked her intended purpose and she stated “jumping”. I THEN looked up at this amiable, agreeable, loves everybody gelding and his pigeon toed conformation. My examination was at that moment finished. Even if he made it over the jumps, it would ruin his front limbs and quality of life so quickly it wouldn’t be fair to the horse, let alone the owner.

Next we should consider proper shoeing and how that impacts your horse’s limbs (especially the lower joints). A quick rule of thumb is this: In a normal foot, the front of the hoof wall, the pastern and the hoof wall at the heel should all have the same angle when viewed from the side. Likewise, a line through the cannon should reach the ground just behind the heel bulbs (see Figure 3).

Figure 3

It is important to remember to keep your horse trimmed regularly, keeping the hoof pastern axis at a correct angle so extra forces aren’t being exerted on your horse’s joints. I’m constantly amazed at the number of owners who schedule a lameness examination and when I go out to evaluate the horse they are 5 weeks overdue on their shoeing. We examine as much as we can but I really hate going through a lot of diagnostics when an obvious problem slapped me in the face just with a visual examination. Again, it’s all based on balance and working with the horse’s conformation that he was born with. The most common abnormal foot shape I see is usually the long toe and low heel. In this abnormality, you lower the hoof-pastern axis creating extra pressure at the heels, the back of the joints and increase fetlock overextension during exercise. Overtime, this shape can likewise also contribute to quarter cracks and navicular syndrome. The most common cause of the foot shape being created is inconsistent or prolonged shoeing intervals. Increasing the interval between shoe applications can result in the heels overgrowing the sides and back of the shoe as the shoe is drawn forward by the lengthening wall at the toe. This leads to separation, cracking and chipping of the wall at the heels, which encourages the formation of this foot shape. A regular shoeing interval CANNOT be emphasized too strongly. Does basic husbandry ring a bell?

Exercise is another important aspect of joint health and helps properly condition all of the parts of the musculoskeletal system – bones, joints, tendons, ligaments and muscles. Exercise is important in maintaining joint function and mobility. Activity improves blood flow to the soft tissues of the joint and it also increases the elasticity of these tissues. Likewise, exercise moves the synovial fluid around the joint space (which nourishes the cartilage) and improves the rate and quality of synovial fluid production. Daily pasture turnout is preferable to stall confinement, and even those horses that are quiet out in pasture should be worked daily even if it only involves light longeing for 10-15 minutes twice a day. Again, basic husbandry is waving his hands and jumping up and down.

Exercise can also affect a horse’s joint health in more specific ways. The time to begin formal training is another milestone that can affect a horse’s joint health as they grow older. Too much strenuous work prior to the growth plates closing can predispose a horse to injury. Excessive, repetitive motions when horses are too young can excessively wear on tender cartilage and damage bone e.g. constantly longeing in small tight circles or turnout in only a small paddock that causes young colts to run and stop and turn abruptly over and over. Bad habits can affect a horse’s joint health e.g. a horse that weaves in his stall (shifting his weight back and forth over and over on his front legs) can cause wear and tear on the outside of the front legs due to the constant sliding motion. Muscle fatigue occurs more quickly in under-conditioned or poorly-trained horses. The horse that stands around all week and then is made to do a week’s work in a day is more likely to develop joint (and other musculoskeletal) problems than the horse that is exercised more often. Likewise, allowing a horse to become or remain overweight can add to the compressive load on the joints. Most of the above examples are again based on basic husbandry (do you notice a trend here?). But in the end, strenuous exercise is often the main cause for degenerative joint disease (DJD). Although the joint does have some capacity to heal, we need to make sure there is a healthy balance between the damage and the repair. Not allowing the joint enough time to repair accelerates the degenerative process in many athletic horses.

Specific exercise disciplines can also allow you to narrow down where you may have future problem with degenerative joint disease. For example, Quarter Horse and Thoroughbred racehorses are more prone to knee and fetlock problems because of the extreme overextension in these joints during galloping and the fact that most of these horses are young and their entire musculoskeletal system is relatively immature. Horses involved in western sports (roping, barrel racing, reining, etc…) are more prone to hock and pastern problems. Quarter horses often have a more upright conformation which adds to the concussive and compressive load on these joints during strenuous activities. Also the extreme forces these joints must withstand during sharp turns, spins and sliding stops contribute to most of the joint disease seen in these horses. You are more likely to see hock problems in dressage horses (any breed), Saddlebreds and Standardbred race horses as they often have exaggerated hock motion during their competitions. So as you can see, the breed and their use can also be considered when trying to pinpoint potential problem areas and you can tailor your husbandry methods to help protect them.

In most cases, degenerative joint disease is caused by wear and tear of the joint’s soft tissues and cartilage surfaces. The two basic elements of DJD include synovitis (inflammation of the synovial membrane and pad) and cartilage degeneration. Persistent or repeated synovitis can degrade the joint fluid (remember the synovial membrane produces this fluid and if it’s damaged, the fluid production and quality is likewise damaged) making it thinner and a less effective lubricant. It also becomes less effective at protecting the cartilage surfaces from harmful inflammatory substances that are being released. Now the weight of the horse (and rider and tack) compresses the cartilage. Speed, landing after a jump, sudden turns or stops, etc… can intensify this effect. Repeated compression causes the cartilage to become roughened, flattened and less resistant to compression which causes damage to the cells of the cartilage. These damaged cells release enzymes that degrade cartilage even further making it prone to physical damage. These enzymes also cause more synovitis when it leaks into the joint fluid. These two components, inflammatory substances and compression, creates a vicious cycle: flattened and eroded cartilage which leads to increased concussion to the underlying bone which leads to greater friction within the joint which leads to chronic pain. (See Figure 4) We've already affected the soft tissue with joint capsule fibrosis (A) and synovitis (B). Now, as it starts affecting the bone you end up with decreased joint space (E), new bone production on the edges of the joints (C) and a remodeling (different shape) to the bone (D).

Figure 4

When I can actually see bony changes on a radiograph, we are looking at the “end” of the condition; the irreversible conclusion to joint disease. That is why we would rather treat preventatively before bony changes occur.

Then what exactly should we be looking for if we are looking for evidence of joint disease? Clinical signs can include joint swelling, palpable heat in the joint, reduced range of motion through a joint, pain during flexion of the joint, and the most common complaint: lameness. Most often owners will take clinical signs such as these and treat with rest, handwalking, and anti-inflammatories which often give positive results. However, in general, if the lameness and joint swelling persist or return (even after improvement) with continued work or return to work, it is usually safe to assume that the changes within the joint may include cartilage degeneration. If degeneration is present, let’s discuss some things we can do to help out our horse’s joints medically.

Medical therapy for overall joint health will be based on the amount of changes we have in the horse already. For a horse that has been an athletic, performance horse for some time versus a young horse who has been a pasture and trail horse all his life, obviously the joint changes could be profoundly different. Commonly used joint disease medications include:

NSAIDS – This stands for non-steroidal anti-inflammatory drugs and includes medications such as phenylbutazone (bute), flunixin meglumine (Banamine®), ketoprofen, etc. These medications assist by reducing inflammation to allow healing to occur and likewise help with pain. These medications do well when used appropriately and any underlying causes are likewise brought under control. Consistently using these medications long term just to hide pain is an inappropriate use of these medications and long term use may cause side effects. These medications likewise can be detected in pre- or post-competition drug screens.

PSGAG – This stands for polysulfated glycoaminoglycans and includes medications such as Adequan®. These medications protect the cartilage (chondroprotectant) and help prevent the development of joint disease and slow its progression.

HA – This stands for hylaronic acid and includes Hylavet®, Hylartin-V®, Legend®, etc… This is an essential element in the normal joint fluid and cartilage. It can be administered intravenously as well as intra-articularly (directly into the joint). HA minimizes damage from inflammation within the synovial membrane and cartilage.

Corticosteroids – This includes medications such as Depo-Medrol®, Vetalog® or other cortisones directly injected into the joint. These are very powerful anti-inflammatory drugs and are often used in combination with HA injections. Select corticosteroids can also show a protective effect on the cartilage (chondroprotective) and enhance the healing process within the joint. These medications likewise can be detected in pre- or post-competition drug screens.

Chondroitin / Glucosamine / Manganese Combination Products – Although this is a “type” of nutritional supplement which we will discuss in the next grouping, I wanted to give it their own separate grouping for better explanation. This category includes the product Cosequin®. The ingredients include the following: Glucosamine HCL – It’s a building block for the production of glycoaminoglycans and hylaronic acid. The primary function of glucosamine is to stimulate the secretion of glycoaminoglycans in the articular cartilage; Chondroitin Sulfate - In addition to being the major glycoaminoglycans found in cartilage, its primary function is to fight against degradative enzymes that contribute to cartilage breakdown; Manganese – Another building block in the body for the production of glycoaminoglycans; and, Ascorbate – A building block in the body for collagen production. One of the main reasons I gave this product a separate subset is because Cosequin® has been through the rigors of scientific testing and is scientifically proven to work.

Nutraceuticals – This is a name used for all the joint supplements that are available on the market. It’s a subset, if you will, of pharmaceuticals that deal specifically with nutritional type of medications. For a horse with no specific joint or lameness issues a good joint supplement may be all that is in order. Any of you who have looked in any equine supply / tack magazines will know that there are about 10 pages of supplements you can choose from. Two main ingredients you should try to include in your horse’s joint supplement would include chondroitin sulfate and glucosamine. The reason I separated it from Cosequin® is that most of these products haven’t had any scientific testing performed and are simply basing their ingredients on other proven products with similar ingredients. In theory, yes, you can say that it seems like sound reasoning; however, some of these products in different formulations (e.g. an acetate rather than a sulfate) may not be as available to a horse as others. In other words, they may waste a large portion of the product if the body can’t absorb it in its current form.

Sometimes the lameness issue needs to be better identified with a lameness evaluation and radiographs. In general, for a horse with lameness issues already, injections of hylaronic acid directly into the worst joints may be in order with follow up joint supplements for the body. In certain horses, we may treat with anti-inflammatories prior to and after certain athletic events while maintaining with a joint supplement. Keep in mind, in an aged, arthritic horse an “athletic” event may be a farrier visit. If you have been fighting with your normally level headed aged horse during your farrier visits--keep in mind he may be sore in his joints. Most farriers will point it out to you and maybe suggest a visit from your veterinarian for further evaluation.

Remember, in the end, good joint health should be a “joint effort” all around. Good husbandry practices, adequate turn out, regular exercise, protective joint supplements and lameness diagnosis will keep your horse in the best working order possible. And never forget, an injured or diseased joint is part of a bigger picture… YOUR HORSE. If training is inappropriate, farrier work inadequate or athletic goals unreasonable… no veterinarian, prescription drug or supplement will solve the problem.

Does He Measure Up?

So you have been pondering the great question, “Should I breed my mare?” I’ve had several clients lately discuss some pros and cons of breeding, in particular with cooled semen. For those of you who don’t know the scoop, cooled semen is pretty much just what it sounds like. A stallion, in another state from around the country, will be collected, the semen will be “extended” with a product that will help protect it and give the sperm nutrients to live on until it gets to your mare, then the product is cooled and shipped to your mare for insemination. We won’t get into all of the logistics of breeding your mare in this article (but I do sense another article in the works) but as you could probably tell there could be some problems in the breeding process if you picked a stallion that didn’t have good quality semen or pregnancy percentages. One of my clients asked me specifically in an email what questions she should ask the breeder now that she had her stallion choices narrowed down to a few. As I replied back to her I decided that it would be a good informative article for most of my clients as well. Here are some important questions to consider prior to picking a stallion for semen transport:

  1. What are the days they ship the semen? For example, if they only ship 2 days a week it is harder to get the mare to ovulate when we can get the semen. Oftentimes it’s every other day. Do they ship on the weekends?
  2. How soon before needing the shipment do they need to be informed? Some require over 24 hours notice… some require by a certain time in the am the day of, etc...
  3. What is the stallion’s first cycle conception rate? i.e. what is the percentage of mares that get pregnant off the first AI breeding? Hopefully yours will be at least 60%.
  4. What is the percentage of mares that got pregnant from total attempts last year? They should have those numbers available.
  5. What is their policy on multiple breedings per collection? Do they have a number of “in house mares” that get first bidding or will we definitely get an appropriate amount of semen when we request it?
  6. Also look in to policies regarding if we do need to rebreed during the same season. Most places will charge you a collection fee and a shipment fee each time. Make sure they aren’t out of the ordinary cost wise.

Did You Know?

Researchers are currently pursuing a goal that would allow a blood sample to predict the future bone and joint health of a horse. Yes, that is what it sounds like. Someday in the future, part of a prepurchase examination could actually include a blood sample to help you predict how your horse’s joints will age and if he would be afflicted with degenerative joint disease or other musculoskeletal problems. Amazing, huh?

Accounts Receivable

Due to a fair amount of clients abusing my good nature, we are going to have to make a few financial changes at Greener Pastures Veterinary Clinic, Inc. Some of you may have noted that we are currently not accepting non-client emergencies anymore due to an abuse of my personal time by horse owners who do not utilize me for routine services. Likewise, with the recent increase of clients carrying longer term balances without appropriate consistent payments, we will be making every attempt to collect money at the time of the service. Please take this into consideration especially in boarding barn situations, as we may refuse service if payment is not present on the day of barn work. We apologize to take up this space in our newsletter for all the clients who keep their balance paid off.

Classifieds

A classified from The Roundup from Burns, Oregon (as read in Reader’s Digest, Dec 2005): “For Sale: One kid’s pony saddle and bridle $400. Comes with free accessories, smashed pony cart, broken harness and one evil pony.” Okay is it just me…or could a number of my clients have submitted that same classified in a local paper here?