Joints are in a steady rate of degradation from the moment that a horse stands and walks. As much as we would like to think that our horse will be an exception to the rule, the fact is that almost all horses will experience some degree of osteoarthritis as they age.
Osteoarthritis is the inflammation and subsequent bony changes that occur as a result of damage to the cartilage padding the ends of bones in joints. In mild cases of osteoarthritis, simple measures can be taken to slow joint degradation, curb the pain, and improve a horse's performance capabilities. Weight loss, increased turn-out, liniments and oral joint supplements are common first-line defenses used to combat joint pain.
As osteoarthritis progresses, more aggressive therapies ? such as injectable joint supplements and acupuncture ? often keep the horse going. But, when the wear and tear pushes joints to their limits, vets start getting serious about joint therapy. While some treatments ? such as tildren, interleukin receptor antagonist protein (IRAP) and acoustic shockwave therapy are effective ? they?re expensive and difficult to find. So, one mainstream direct therapy for aching joints is corticosteroids. While intra-articular corticosteroid therapy is tried-and-true in that it makes horses sound, it isn?t without drawbacks.
Not a ?Lube Job?
As much as most horse people want to skip to the punch line, this is one instance in which understanding what corticosteroids do in a joint is essential. Without this knowledge, you simply can't make a sound decision for your horse. Many horse owners can be misled into thinking that corticosteroids simply provide a ?lube job? for damaged joints. This is simply not true. They?re working in a far different manner.
Corticosteroids injected into a joint primarily act as potent, long-lasting anti-inflammatory agents. They achieve this effect by inhibiting the tissues within the joint from releasing several chemical mediators that cause the signs of inflammation, which are heat, swelling, excess fluid, pain and loss of use.
Although technically any corticosteroid can be used in any joint, vets definitely have their favorites for each joint and for each degree of osteoarthritis. Our chart on page 7 shows the common uses, dosages and costs.
The benefits of corticosteroids are numerous:
Horses that have been lame for years with osteoarthritis pain become sound within hours of a corticosteroid injection.This occurs because corticosteroids work quickly and efficiently at the cellular level to stop cells from releasing inflammatory mediators.
Just about any joint can be injected,including the temporomandibular joint (TMJ), the vertebral facets in the neck and back, the sacroiliac joint, hocks, stifles, knees, fetlocks, pasterns and coffin joints. They?re even used in bursas (fluid-filled shock-absorbing sacs) and in tendon sheaths.
Joint injections usually provide palliative, or soothing, relief for several months. Corticosteroids bind so exquisitely to enzyme-producing cells that their effect is immediate and irreversible. Once the cell that produces inflammatory chemicals is bound, it can't release the harmful inflammatory mediators that cause all of the physical signs associated with osteoarthritis. Of course, eventually the cortisone level diminishes in the joint, which leaves the cells free to create inflammation again.
Compared to many other therapies, joint injections are relatively inexpensive. Joint injections can cost as little as $100 per joint and max out at $800 in some instances (such as difficult hock or stifle joints.) But if one considers that this therapy performed just once can last for several months, the cost per day begins to seem quite reasonable.
Joint injections save time and money,as they can cut down on the need for physical therapy and supplemental treatments, such as chiropractic work, acupuncture, massage, stretching, and joint supplements.
In most instances, horses won?t test ?positive? at shows when they have corticosteroids in their joints.The exception to this rule is a horse that is injected within days of a competition since potentially joints injected within 10 days of competition can result in positive blood tests (always check your rule book to be certain).
Even horses that aren?t necessarily lame per se are commonly reported to move better following joint injections.Horses that receive corticosteroids in their joints have been reported to show larger strides, fuller range of motion of joints, more strength and stability in their movements, and better focus in training.
We can't overlook the drawbacks to corticosteroid use: Any time a veterinarian inserts a hypodermic needle into a joint space, there is a potential that the needle will carry bacteria into the joint.
The risk is low, mainly because vets are methodical about using sterile techniques. Some often additionally safeguard the horse by injecting antibiotics into the joint along with the corticosteroids.
Regardless, the chance of joint infection still exists. If a joint becomes infected, permanent lameness or even death can result. In most instances, the joint will have to be surgically flushed, which can cost thousands of dollars. It usually takes seven to 10 days for the horse to show signs of infection.
Another potential (albeit rare) complication of corticosteroid joint injection is laminitis, which can result in long-term lameness and in many cases, euthanasia.
Some brands of corticosteroids are fabled to be more likely to cause problems in horses, although recent statistical studies have disproven this notion. One thing is for sure, the more corticosteroid a vet injects into a horse, the more of a chance that horse has of foundering.
The amounts presented in the chart below are believed to be the maximum ?safe? levels of corticosteroid that a vet can inject at any one time. However, these levels are debatable, as some vets use higher amounts safely.
Osteoarthritis occurs because the cartilage lining the ends of the bones becomes damaged and eroded as a result of repetitive trauma. Since cartilage has a poor blood supply, it's slow to regenerate once it's been damaged. The body?s natural defense mechanism to stop itself from damaging the cartilage further is to create pain and inflammation in the joint to stop the joint from being used. Pain is a constant reminder to the body as it says, ?Hey...I am damaged here...please don't use me until I can heal!?
If horse owners ignore these signals and force their horse to keep working when cartilage is damaged, eventually the cartilage will break down to the point where the underlying bone that it is covering is exposed. The bone reacts by remodeling (usually to produce a callous or ?spur?). Once that process starts, it's irreversible and will continue to worsen over time.
With that in mind, it seems logical to inject corticosteroids into arthri
tic joints. Why' If we know that the osteoarthritis is degenerative (meaning that it will only get worse with time) then injecting corticosteroids seems like a great option to improve the quality of a horse's life by stopping pain and restoring use of the joint. And indeed it is. However, in a way, corticosteroids also contribute to the demise of the joint by blocking the pain and inflammation that is associated with the damaged cartilage. Without that mechanism there to stop the body from using the joint, the rate of joint deterioration will accelerate since owners will continue to create trauma in the joint by riding the horse. So, where is the Catch 22'
Choosing injections so that your horse can be comfortable on a daily basis rather than have them live a long life of pain due to osteoarthritis makes sense. You just need to be aware that the slippery slope starts with the first injection, because from then on, it's difficult to stop periodically injecting the joint since its rate of demise will accelerate as a result of overuse.
One other hitch in the corticosteroid-use get-along is the three- to seven-day rest period required for the horse after a joint is injected.
The reason for this is twofold. 1) Restricting use immediately after joint injection gives the corticosteroid a chance to really establish itself in the joint and knock down inflammation. 2) Research shows that during the first few days following joint injection, corticosteroids stop the regenerative (or healing) abilities of cartilage.
This effect is transient, but it's important to protect the cartilage during the first few days following injection because although the horse can feel fantastic, it can do more damage to the joint by doing too much too soon.
When all is said and done, owners and their veterinarians carefully weigh the risks and benefits of corticosteroid joint injections. Most owners try to exhaust other avenues of therapy prior to joint injections, and in some cases, these methods will work for a while. Where the rubber hits the road, most horse owners opt for a functional, comfortable and usable horse over a lame one. Therefore, corticosteroid joint injections remain a popular and successful remedy to combat joint pain in virtually all riding disciplines.