Equine Arthritis

Equine arthritis, otherwise known as degenerative joint disease, is the most common cause of lameness in horses. While older horses are often affected, arthritis can strike at an early age, too, altering a promising career path. Let’s look at what arthritis is and how to deal with it.

Cycle of Inflammation

A joint is comprised of two bones that need to move independently of each other. A cartilage layer on the ends of each of those bones acts as a shock absorber, and joint fluid facilitates movement and also absorbs shock. A joint capsule holds the joint fluid in and keeps the bones together. It’s a very simple design with many complicated features. And the greater a joint’s motion is, the more susceptible it is to problems.

Joint inflammation is the body’s way of trying to fix a problem. The problem usually starts off as some sort of tissue damage or infection. Inflammatory cells, which are white blood cells, move into the area and start a whole cascade of reactions. These inflammatory cells do a great job killing bacteria and absorbing damaged tissue, but they also release chemicals into the surrounding tissue that actually destroy it. This is where arthritis can develop—and this is why inflammation is so destructive and why we do as much as possible to stop it.

Over time, the self-feeding cycle of inflammation results in joint surface (cartilage) deterioration, painful joint capsule thickening and the break down of joint fluid. The body, in an attempt to heal the damage, lays down scar tissue and bone that decrease flexibility and overall joint function.

All of the above are also very painful. As cartilage is destroyed and the underlying bone becomes unprotected,  it hurts. Some of the chemicals released by inflammatory cells actually stimulate pain. This is the body’s defense mechanism, designed to stop the horse from using damaged tissue so it can heal. Unfortunately, in the case of arthritis, all this accomplishes is further break down of the joint due to decreased circulation from inactivity.

Arthritis Management

There are several areas of prevention and management that focus on stopping the inflammation and supporting the structures of the joint, including proper trimming/shoeing, exercise, good footing, balanced nutrition, injections and responsible breeding. New therapies are being investigated that are aimed at stopping cartilage destruction, but arthritis prevention is the best treatment of all.

Exercise

A great natural anti-inflammatory is circulation. Increased circulation improves the body’s ability to remove toxins produced by inflammation cells, and therefore decreases joint damage. Increased circulation also removes fluid from the inflamed tissue and increases joint mobility.

Increased circulation occurs with exercise. The simple act of walking increases blood flow. Often, arthritic horses will start out “stiff” during work, but warm up after a period of walking.

Regular exercise routines are key for arthritis prevention and management. Turnout paddocks and pastures are great for constant walking to keep joints limber. Daily riding also helps prevent and treat arthritis.

The amount and type of exercise should be tailored to the horse’s ability and conformation, and the footing should be considered. Hard, rocky footing will add more concussion to the legs, so good footing is preferred. This means riding in well-maintained arenas; when trail riding, walk the hard, rocky stretches and save trot/canter exercise for nice parts of the trail.

Fitting the horse’s career to his conformation is also very important. Horses with poor conformation, such as toed in, toed out, sickle or cow hocked, upright pasterns and straight hind legs are more prone to arthritis due to abnormal concussion on the joints. These horses can often perform while young but are at greater risk of developing arthritis. Therefore, the type of work they do should be carefully chosen. A wise trainer or rider will keep these horses at lower levels of competition, even though the horse may be more talented, in an effort to preserve the joints.

A great example of career choice based on conformation is the western pleasure horse, which is typically bred to be straighter in the hind legs. This type of conformation allows the western pleasure horse to perform the soft jog and lope required for the sport. However, a horse built for western pleasure would have much difficulty doing extended and lateral work required for dressage. These horses can do other types of work but tend to have poorer performance and are at more risk of developing problems sooner in life.

Trimming/Shoeing

Trimming and shoeing are very important in both the prevention and management of arthritis. Improper trimming can cause abnormal concussion on the joint. The most common error is uneven trimming, with one side of the hoof higher than the other. This imbalance causes one side of the hoof to land first and creates increased concussion on one side of the joint. Over time this can develop into a type of arthritis most commonly known as ringbone.

Long toes/low heels are also bad for the joints, causing added stress on the joints from the increased breakover. Overall, horse owners should strive for balanced trimming from side to side, and keeping the toe short. For horses with hock arthritis, I like to see the hind toes squared off so the leg can roll over the toe easier, decreasing the stress on the front of the leg and the hock.

Supplements

Joint supplements offer management and prevention at once. There are many products available aimed at stopping joint cartilage breakdown by supplying the body with the building blocks for cartilage production. These building blocks—chondroitin sulfate and glucosamine—are the main molecules supplied in these joint supplements.

There are also many herbs available; the two most common anti-inflammatories are yucca and devil’s claw. The effectiveness of these herbs is questionable, but many horse owners report good results for their horses when used for low-level arthritis.

Joint Injections

The tried-and-true management strategy for arthritis is joint injections. The main goal of this therapy is to reduce the inflammation within the joint and help restore it to a more healthy state, therefore reducing pain and returning the horse back to his regular exercise routine.

Most joints are injected with a corticosteroid along with hyaluronic acid. Corticosteroids are very strong anti-inflammatory drugs that break the cycle of inflammation. Hyaluronic acid is synthetic joint fluid that replaces the weak, thin, joint fluid that is no longer doing its job. There are many types of corticosteroids used for joint injections, but the most common are betamethasone, Depo-Medrol and triamcinolone. Triamcinolone has been shown to be chondroprotective when used in small doses; this means it actually helps produce stronger cartilage and thicker joint fluid.

Intramuscular and Intravenous Injections

Hyaluronic acid is also available in an intravenous preparation under the brand name Legend. When given intravenously, it migrates to the joint and stimulates the joint to produce more joint fluid and also acts as an anti-inflammatory drug. (HA is also available in oral supplements, but research on efficacy is still pending.)

Polysulfated glycosaminoglycan (Adequan) is available in an intramuscular preparation that helps strengthen the cartilage and also stimulates the joint to produce more joint fluid.

Non-steroidal anti-inflammatory drugs (NSAIDs), such as bute and Banamine, are also used to help alleviate pain and decrease inflammation within the joint. This class of drugs has some side effects, such as ulcers, kidney or liver damage, if not used cautiously. In an effort to avoid side effects, a topical cream called Surpass has been developed. It acts as an anti-inflammatory at the site where it is applied.

Personal Notebook

In my practice I deal mostly with hock arthritis and ringbone, with a few knees thrown in for good measure. I work with the owner to develop a tailored program based on degree of lameness, degree of arthritis determined by radiographs (X-rays), career of the horse and the resources available.

Horses with mild hock arthritis are usually not lame but rather have performance problems, such as not striding out, swapping canter leads, difficulty picking up correct canter leads and refusing jumps. For these horses, oral joint supplements, intravenous Legend and intramuscular Adequan are the first line of treatment if the horse is in low-level work, such as trail riding.

I also try to make sure the horse is not spending too much time in a stall, and I encourage daily turnout and under-saddle exercise. In many urban areas pasture is not available and horses are stabled in stalls. Spending time standing in stalls leads to problems. Horses that walk around all day in turnout keep their joints healthier due to increased circulation.

Athletic horses that suffer arthritis usually need joint injections to return them to the level of work they were at or to resolve lameness. Depending on the amount of work the horse is doing and the severity of arthritis, the joint injections usually only have to be done once a year. Concurrent use of Legend, Adequan and oral joint supplements (chondroitin sulfate and glucosamine) help prolong the duration of the joint injections. Squaring the toes of the hind hooves and setting the shoes a little back from the toe eases breakover—allows the toe to roll over faster—and therefore reduces the stress on the joints.

Many performance horses are given oral joint supplements, intravenous Legend and intramuscular Adequan as preventative care in an effort to stop or minimize joint damage created by the demands of high-impact sports. This regimen also helps keep the performance horse as comfortable as possible. By keeping arthritis pain in check and keeping the horse moving as much as possible, we also help prevent secondary injuries, such as joint sprains, tendon injuries and sore backs.

Show horses in full competition often receive Legend and Adequan shots monthly, while others get the shots quarterly. Once again, all of these programs are tailored to the individual and depend on response to treatment.

New Horizons

There are some wonderful scientific minds out there trying to find solutions to what causes arthritis and how to fix it. The current focus is on extracorporeal shockwave therapy; drug therapies; chemicals released by inflammatory cells; and the cellular structure of the tissue that make up the joint.

ESWT
Extracorporeal shock wave therapy (ESWT) is a treatment that has proven to work very well for equine arthritis. It has been around for a decade, but over the last few years has been clinically proven to resolve lameness due to arthritis. At this time it is unknown how exactly ESWT works, but it’s a very active field of research. The research has so far proven that arthritic horses do respond positively to the treatment, and many prominent clinicians are recommending it. There had been some concern that ESWT causes microdamage to the bone tissue, leading to fractures. Thankfully, current data doesn’t support this theory.

Drugs
Tildren, a new drug that’s being used in Europe to manage arthritis and navicular disease, stops the breakdown of bone. No word yet on when this treatment might be available in this country.

Chemical Mediators
Research examining the bad chemicals that trigger tissue damage, as well as the good chemicals that stimulate tissue development, is hot right now and may revolutionize management and prevention of arthritis. Gene therapy is a related topic, with researchers hoping to find a way to introduce genes that stimulate joint cells to produce joint-friendly proteins, create synthesis of cartilage and block formation of destructive enzymes.

Tissue Transplants
For years researchers have been trying to transplant cartilage to restore damaged joints. So far they have been unsuccessful, but they are still trying. Cell transplants into the joint or cartilage to stimulate tissue production are also being studied. This is extremely encouraging and would be less invasive than actual tissue transplants.

All of these areas of treatment are showing great promise and some successes. In the last 10 years we have advanced dramatically in the recognition and management of arthritis. In the next 10 years we can expect to see more great advancement in the prevention and treatment of this debilitating disease.

Further Reading
HorseChannel’s Joint Care Guide

This article originally appeared in the October 2005 issue of Horse Illustrated. Click here to subscribe.