The bone surrounding an arthritic joint can react to chronic inflammation. Extra bone begins to be deposited at the edges of the joint. This produces little spurs of bone, as seen in these radiographs.

Arthritis is both overdiagnosed and underdiagnosed in horses today. It’s overdiagnosed when a cause of pain other than joint disease is making your horse move stiffly or be sore. And it’s underdiagnosed in the sense that early signs of arthritis often can be missed, leading to a delay in treatment at a stage when action is most likely to be helpful to your horse.

Horses are masters at compensating for relatively mild joint pain by redistributing their weight. The end result of this method is that your horse with early arthritis will often not be noticeably lame.

Signs of Arthritis
There will always be increased temperature/heat over early joint inflammation, but unless it’s more than a five-degree rise you won’t be able to feel it with your hand. Thickening of the synovium—the lining of the joint—is always present and fluid within the joint will be increased to varying degrees, but these changes may only be detectable by an experienced veterinarian. Nevertheless, heat and joint swelling/puffiness are things you should train yourself to check for on your horse regularly. If you’re familiar with how your horse normally feels, you will be much more sensitive to any changes.

More subtle signs that something is bothering your horse include:

• shortened stride front or hind
• "stiff," rigid feeling through the back
• change in head carriage (up or down)
• more rigid head carriage (less up and down movement)
• decreased willingness to trot or canter
• preferring one diagonal or lead over another
• reluctance to turn to one side
• difficulty with circling/lunging
• difficulty going up or down hills
• development of vices or spookiness under saddle or laziness/sluggishness and unwillingness to work
• resistance to being tacked up
• flinching or moving away if you touch or brush over a joint (very common with stifles especially)
• uneven hoof or shoe wear
• preferentially resting a leg when standing or standing with the leg in an abnormal position. This includes pointing or standing with leg too far under in front legs, resting or rotating leg to the outside in hind legs.

More accurately, these are all signs that your horse has pain. If you notice any of these symptoms, get your veterinarian involved sooner rather than later. The more quickly you identify the problem, the sooner you can deal with it.

As the arthritis progresses, the symptoms listed above increase in severity and other changes commonly occur. The size of the hoof on the involved leg will often become smaller over time. As a result of uneven loading of the limbs in an attempt to unload the sore one(s), muscle bulk in a sore leg will become less developed over time, while the legs that are compensating for this by taking more of the load develop more pronounced muscles. Back muscle stiffness and even pain to the touch is also very common in horses with arthritis, both front and hind legs.

A hallmark of chronic arthritis is stiffness when your horse first starts to work, which gets better after a warm up. The amount of time it takes to warm up your horse also commonly increases. This stiffness has several causes. One is a stiffening of muscles, causing shortening of tendons, in the leg. Another is that soft tissues around the joint lose some of their flexibility over time when your horse has not been loading them normally.

The Role of Joint Nutraceuticals
Joint supplements can be effective in reducing the pain of arthritis, but a lot depends on exactly what is going on in the joint—what stage the arthritis has reached. Arthritis often begins as inflammation of the synovial lining of the joint and progresses to softening and thinning of the cartilage, which leads to cartilage loss. The bone surrounding the joint also can begin to react to the inflammation. Extra bone begins to be deposited at the edges of the joint. This produces little spurs of bone in the joint and can progress to where bone actually extends across the joint to meet the bone on the other side. That process is called joint fusion and it’s the body’s way of stopping movement so that the inflamed area doesn’t become further irritated.

As a rule, the joint nutraceutical ingredients hyaluronic acid, chondroitin sulfate, and glucosamine work best during the early stages of arthritis. Their best-documented effect is actually anti-inflammatory in nature. It’s also possible that they may at least slow the loss of cartilage, but their ability to heal areas already damaged is questionable. These ingredients are worth trying at any stage, but are likely to be less effective with advanced arthritis.

A new supplement is avocado-soy unsaponifiables (ASU). These ingredients are fatty acids normally tightly bound to the fiber fractions in soybeans and avocados, and they’re not very digestible. When purified, however, they have been found to have joint preserving properties. That is, they can slow the loss of cartilage in arthritic joints. ASU had no effect on lameness in the experimental arthritis model in horses where they were tested, but the ability to protect cartilage is an important effect.

The benefits of other types of fatty acids, such as CMO or Celadrin®, and of products like hydrolyzed collagen, are less well established. Making sure to include generous levels of omega-3 fatty acids in the diet is likely important to horses with arthritis because a deficiency of these essential fats, or an overabundance of the omega-6 fatty acids, can worsen inflammatory reactions.

With very advanced arthritis, the horse will likely need more help than what these nutraceuticals can offer. Nonsteroidal inflammatory drugs may be needed from time to time, but should be limited because of the potential side effects in the intestinal tract and the kidneys. Liniments and wraps for involved lower leg joints can minimize stiffness. Magnetic wraps can help with pain for some horses.

Is Arthritis Inevitable?
So, in any horse who is ridden even half-way hard, is the development of arthritis a given? The answer to this is no. There are active horses who live to a ripe old age and experience no problems with arthritis.

While arthritis sometimes develops as a result of an injury, and aging does make the joints more susceptible, there are also many risk factors within your control. These include not letting your horse get too fat, avoiding hard work at an early age, and making sure your farrier trims or shoes your horse correctly. If you do your best not to unnecessarily put your horse at risk, learn to recognize the early signs of joint inflammation, and treat your horse early on, arthritis need not be a serious issue.