Friday, May 20, 2011

Demystifying Joint Injections: When they should (and shouldn't) be used

Although the horse is an animal abundently gifted with speed, strength and agility, it was never designed to fly around barrels, slide 40 feet, or cut cattle at lightning speed. Selective breeding has certainly improved our horses’ ability to perform such feats, but it has not made them better able to withstand the physical stresses that training and competition demand. The inevitable wear and tear is particularly tough on joints, leading many of us to turn to joint injections in an attempt to regain or maintain our horse’s competitive edge. Some are even using joint injections on horses that are perfectly healthy, believing that doing so can help prevent joint problems from developing. Yet despite the fact that the use of joint injections has become almost routine in some circles, many horse owners are confused or uncertain about what joint injections can actually do, and when they are truly appropriate. If this sounds like you, here are some facts to help you separate the truth from the misinformation.


What they do

            Most often, pain in the joints is the result of inflammation, which is itself a response to trauma or disease. But while both pain and inflammation are an attempt by the body to protect the damaged joint and facilitate healing, inflammation can actually be harmful to joint cartilage. This is due to the actions of inflammatory mediators, which are molecules released by the immune system to amplify the immune response or destroy foreign substances. As Antonio Cruz, DVM, MVM, MSc, DrMedVet, DACVS, DECVS, of Paton & Martin Veterinary Services in Aldergrove, BC, explains, “Some of the inflammatory mediators are fairly nasty in a way. One of the main actions they have is to degrade the articular cartilage matrix. Of course there are degrees – you can have a little bit of inflammation, and that’s probably not going to cause much of a problem. However, if you have severe inflammation and it goes unattended, it can potentially lead to osteoarthrosis, which is a degeneration of the joint. Controlling inflammation is therefore one of the primary goals in the use of intra-articular injections.”

            The second goal of intra-articular injections is to restore homeostasis in the joint. Homeostasis is the internal equilibrium between the components of the joint – the cells, tissues, fluid and so on. When any of these components is altered by trauma or a disease process, healing may be compromised and further damage may occur. For example, decreased viscosity of the synovial fluid (the normally clear, yellowish fluid that lubricates the joints) is a common result of joint damage that can lead to further deterioration if the viscosity is not restored to a more normal level.

            Because of their ability to reduce inflammation and restore homeostasis in many cases, intra-articular injections are useful in the treatment a variety of different joint ailments that fall into the category of arthritis – a broad term that simply means ‘inflammation of the joint’. Joint injections may also be useful in the treatment of arthrosis, which means ‘degeneration of the joint’. Whenever possible, it is important to determine whether you’re dealing with arthritis or arthrosis. “The distinction between the two is often not made,” says Dr. Cruz, “but whether you have an inflammatory process or a degenerative process will determine what products you are going to use for treatment. The products do have a primary, targeted action.”


What they don’t do


            Relieving the pain that accompanies inflammation is another objective of joint injections, but it is important to understand that relieving pain should not be done with the aim of putting the horse right back to work at its usual level. Explains Michael Scott, DVM, DACVS, partner and surgeon at Moore & Company Veterinary Services in Calgary, “Intra-articular injections treat the symptoms of the problem, which are joint inflammation and pain, but they don’t treat the problem itself. The actual problem is usually the horse’s occupation. If horses weren’t doing all these extreme, unnatural movements, they wouldn’t be as likely to have sore joints. Therefore, if you use these medications to treat the symptoms without addressing what caused the problem in the first place, you may be setting that horse up to accumulate additional injury.”

Dr. Cruz concurs on this point, stating, “The vast majority of joint inflammation we see is what we call post-traumatic osteoarthritis – it comes from trauma. We understand exercise as an ongoing trauma to the joint, so usually, the more activity the horse is involved in, the more osteoarthritis you see. As that is the case, joint injections should not be used to make the horse feel better so that you have an excuse to continue exercising it. Joint injections are given for a reason, usually inflammation, and one of the components of treatment for that inflammation is to actually provide a little bit of rest.” Cruz adds that ‘rest’ does not necessarily mean that the horse should not be worked at all or that it can never return to its previous level of performance. However, such things must be determined on an individual basis and will depend on a variety of factors.

There are also certain situations in which joint injections will simply not help, or may actually be harmful. Says Dr. Cruz, “Results depend on the primary problem that you’re dealing with. If the problem is synovitis (inflammation of the membrane that lines the inside of the joint), the results may be very good. However, if you’re dealing with degeneration, the horse may improve in the short term, but then go back relatively quickly to where it was before the injection. Arthritis is a disease in which it is a bit difficult to predict its behavior because there is some individual variation in terms of waxing and waning and the intensity of signs, the same as we see in people. If you have a joint that is in really bad shape, it’s probably not going to be helped much by anything that you do.

“If you have an infection in the joint, any injection of steroids would actually be contraindicated, as steroids decrease the ability of the joint to fight infection, same with Adequan (a non-steroidal medication frequently used in joint injections). If you have something like osteochondrosis, you need to address the primary problem, and if you have a chip in the joint, you’re not helping the horse by just medicating the joint without removing the chip. You would have to do both. The bottom line is that ideally, you don’t use joint injections to ‘patch things up’. What you want to do is address the cause of the problem.”

Even in cases where joint injections have proven to be helpful, they may not continue to work the same way repeatedly. As Dr. Scott observes, “People will sometimes talk about how horses will respond to joint injections for a while, and then the injections ‘stop working’. There is a tendency there to blame the drugs, but that is usually not what is going on. More often, joint injections may be associated with a failure to respond over time because this treatment is symptomatic treatment – it is not curing the cause of the joint disease, which may simply be the horse’s occupation, wear and tear, a traumatic event, poor conformation, or a combination of any of those things. If the horse has been treated and he is able to go back to doing what he was doing, he’s going to put further wear and tear on his joints. Therefore, it’s possible in some cases that the horse won’t respond to treatment anymore because he’s degenerated further and he’s beyond the point where the drugs can help him.”

Whether joint injections can prevent your horse from having a problem in the first place is a matter of continuing debate. “I think that the assumption that you can prevent injury or increase the threshhold for injury with so-called ‘maintenance’ injections is incorrect,” states Dr. Scott. “The drugs that are put into these horses’ joints are not going to prevent injury of normal healthy cartilage and joint tissue. With most of them, their primary action is to decrease inflammation. If the joint is inflamed, then at some level of inflammation it becomes appropriate to treat. But, that should be based on some indication that there is an abnormality, rather than just putting it into a normal joint.” Asked if he believes that maintenance injections are a waste of money, Dr. Scott replies, “It’s certainly a waste of money if there is not a problem, and there is also risk involved in that there is the possibility of infection. It’s a relatively low risk, but it does happen, and when it happens it can have devastating consequences.”

Dr. Cruz is not quite as dismissive of the potential value of maintenance injections, though it’s not something he particularly recommends. “I don’t think the idea of so-called maintenance injection is a black and white topic,” he says. “There are few studies on this, but there are some that suggest that use of maintenance therapy may increase the threshhold for injury. However, the other side of the coin is that if you increase the threshhold for injury, does that mean you’re going to exercise the horse more and increase the chance of hurting it? I think that rather than trying to prevent injury with joint injections, we need to look more at exercise management routines, and we need to realize that the capacities of horses and their tissues are not unlimited. You have to know your horse very well to know what level of exercise is appropriate for that individual at any given time.”


Risks


            Whether you are considering the use joint injections for prevention or treatment, it is important to know the risks involved. As Dr. Scott has mentioned, any injection into the joint carries the risk of infection, though the chance is slight if sterile procedures and proper technique are followed. Many veterinarians choose to further reduce the possibility of infection by including a small amount of antibiotic in the injection. However, joint injections can cause additional problems besides infection. Most often seen (though still relatively uncommon) are ‘sterile flares’, which is an adverse reaction to the injected medication that causes pain, inflammation and possible lameness. Sterile flares are not usually serious, but they can delay a return to training.

            Other issues can crop up with the continual use of certain kinds of joint injections. Explains Dr. Scott, “There is a concept that intra-articular injections are somehow hard on the joints, and that if you use them frequently, the drugs will eventually damage the joint and the horse will be permanently lame. Depending on what drugs you’re using, there is some truth to that. If you put corticosteroids into the joint at an extremely high dose and frequency, those drugs can have a negative effect on the cells within the joint that maintain the cartilage, then have a negative effect on the cartilage in the long run. There is actually a term for that – steroid arthropathy – which is a rather poorly defined term, but it goes along with the idea that too much steroid within a joint can do some harm.”

            Perhaps the biggest risk derives not from the drugs themselves, but from the fact that they are often used without a thorough workup being done and with no firm diagnosis. “If you are not diagnosing the problem,” asserts Dr. Cruz, “you may just end  up masking it by alleviating the symptoms, which could actually make the problem worse. This is a major issue with the use of joint injections.” Dr. Scott also sees this as a serious problem in the industry. He states, “People will inject horses’ joints all the time based on a hunch, or on the owner or trainer deciding that it should be done, or a veterinarian saying, ‘well let’s just inject his hocks’ – when the problem may actually be elsewhere. If a horse is treated with joint injections and no diagnostic workup has been done, there is a high degree of probability that the wrong region will be treated. Furthermore, if you don’t address what is causing the problem in the first place, an underlying condition or something you are doing in your training, the problem is not going to go away.”

Another problem Dr. Scott points out is the tendency among horse owners to assume that joints that have been injected are now ‘good to go’. As he explains, “There is a risk if people have the horse’s joints injected and assume that they’ve done something beneficial, then stop paying attention to whatever symptoms the horse may be showing. They’re thinking that they injected his hocks last month so he can’t be sore behind, but the horse could have all kinds of other problems that are never diagnosed because the assumption has been made that the horse has been treated. That’s something I encounter frequently.”


How to avoid the need for joint injections


While it is not unexpected that an old campaigner might have some soreness in the joints that could possibly benefit from joint injections, the fact is that these treatments are not just being used on older horses. It has become common, in some spheres of competition, to inject horses as young as two or three years old. While many people see nothing wrong with that, Dr. Scott disagrees. “If a horse that young needs joint injections,” he states, “something is wrong with that picture. Either that horse is being worked too hard, brought along too quickly, or it has a weakness or conformational issue that is predisposing it to injury – in which case it shouldn’t be worked like that in the first place. I think we are seeing horses being pushed hard at a young age in many aspects of equestrian sport, especially in the Western industry, and in racing.

“These horses, I believe, sustain injury because their bones and joints are not mature, and they’re not trained in the right way. I think that one of the greatest problems that we see is that the horses don’t get enough intermittent exercise before they’re put under saddle, and then get too much consistent, prolonged exercise once they reach a certain age. They’re just mothballed until they’re two, then all of a sudden they start getting trained day after day without a break when they’re 2 ½ or 3.

“Young horses, from birth up until two, need to run around like maniacs. They need to be out in big fields, going as fast as they can go, they need to be running over hard, rocky ground to make their feet strong and make them agile and coordinated. Many, many people do not allow their horses to do that because they’re afraid the horses will get hurt. What they’re doing is that they’re setting them up for injury in the first year or two of their life in training. Then what happens is that they develop repetitive stress injuries. They’re loading their bones and their joints in the same way day after day after day, they’re not getting enough rest or a chance to recover, and so, once they become sore after six months or a year, all of a sudden along comes the veterinarian and the joint injections. That is the result of the management of the horse from the day it was born.  There is research being produced all over the world to support this.”

Another important factor in keeping your horse’s joints healthy is good hoof care. Says Dr. Scott, “Quality foot care plays a big role, because if the horse has poor foot care, then it has abnormal biomechanical forces acting in the leg that put abnormal stresses on the joints. Many times we can back a horse away from needing joint injections by optimizing his foot care. Any kind of imbalance or incorrectness can cause problems.”

However, there is another issue in regards to the horse’s hooves that may not be correctible through hoof care. “To be successful in some of these sports,” explains Dr. Scott, “the horse needs a small, light foot because if they have a large, robust foot, they can’t move it quickly because of the mass involved. The problem is that a small, light foot that is working hard is more likely to get sore. This is an example of how the genetics that are positive for performance can be negative in terms of longevity.”

Genetics actually play a much bigger role in the likelihood of a horse needing joint injections than many in the industry will admit. While it would be easy to say that it only appears that way because the offspring of certain horses are more likely to be involved in certain sports, the bottom line is that conformation faults and many underlying weaknesses are determined by genetics, and horses with these faults and weaknesses are predisposed to injury. Says Dr. Scott, “I can tell you that there are certain lines and certain types of horses that are much more likely to develop degenerative conditions requiring treatments such as joint injections.”

Dr. Cruz also points out that we need to be realistic in our expectations of our horse’s performance, and not expect them to be at their best all the time. “The pressures of competition are very high,” he says, “and the horses are asked to maintain a peak level of activity for a very long period of time. But there is no high level athlete who can maintain a peak for weeks at a time without any time of intervention. We have to remember that a peak is just that – a peak, not a plateau. It would be best if you could plan your competition season to peak at a certain point, when it is most important to you, but the structure of the industry may just not allow that.”

Therefore, if we want to avoid the need for joint injections, we must take a number of factors into consideration, from genetics and hoof care to how we raise, train and campaign our horses. You may want to think about adopting a training program that incorporates more of a “cross-training” approach in which horses are exposed to different kinds of exercise, interspersed with periods of rest and the chance to move naturally at liberty whenever possible. In the end, we need to remember that horses are not machines with replaceable parts, and joint injections are not the equivalent of an oil change on a car. Joint injections certainly have their place, but they should not be used lightly, and they will never replace good management and humane consideration of what is in the horse’s best interest.


SIDEBAR: Types of medication used in joint injections

           
Joint injections (technically called intra-articular injections) fall into four main categories:

  • corticosteroids (also called cortisone or steroids): There are different types of corticosteroids that have different actions, but as a group, they are the most commonly used medications in joint injections. They are the most potent anti-inflammatories, and they’re also the least costly. They reduce the damage that can be caused by inflammation by inhibiting the movement of inflammatory cells, and they are quite effective at reducing heat, pain, and swelling. On the down side, they can cause damage to joint cartilage if used at high dosages repeatedly.

  • hyaluronic acid (HA, also called sodium hyaluronate, common brand name: Legend): HA is a product produced naturally by the synovial membranes that line the inside of the joints. It provides some lubrication and is believed to protect joint cartilage by inhibiting the action of inflammatory mediators. As a joint injection medication, it is more expensive and has milder anti-inflammatory and pain-relieving effects than steroids. It works best on the more superficial areas of the joint, and on mild to moderate synovitis (inflammation of the synovial membrane). It is also available in an intravenous (IV) form.


  • polysulfated glycosaminoglycans (PSGAG, common brand name: Adequan): PSGAG is believed to help prevent cartilage degeneration by inhibiting the effects of various enzymes associated with cartilage degeneration. While many believe PSGAG is effective in preventing cartilage degeneration in a joint, it cannot heal damage already sustained, and some doubt that it can protect cartilage at all. Study results vary, with some showing PSGAG to have a positive effect, while others showing it to have little value in preventing cartilage degeneration. There may also be a higher incidence of infection and sterile flare associated with the use of intra-articular PSGAG than with other products, leading many veterinarians to use the more recently available intramuscular (IM) form of Adequan. However, some have found the IM version of Adequan to be less effective than the intra-articular form.

  • interleukin-1 receptor antagonist peptide (IRAP): IRAP is a serum made from a sample of the horse’s own blood that has been specially incubated to produce a large amount of the body’s naturally occurring anti-inflammatory proteins. This is then concentrated into a serum that is an effective anti-inflammatory when injected into the joint. One draw of blood generally produces enough serum to make five injections. Best of all, IRAP appears to have none of the potential side effects of corticosteroid medications.

Veterinarians commonly use more than one medication in a joint injection (e.g. a steroid in combination with HA), as the various types of products address different parts of the equation and often work synergistically.