Diagnosing Arthritis in Your Horse

Typically, horse owners seek veterinary care because their horse is lame, or because their performance is not up to par. For example, the owner of a reining horse may say she’s noticing that her horse is reluctant to turn or to slide, or that he isn’t moving as well as he used to. You may notice swollen joints caused by an accumulation of fluid, known as joint effusion. Arthritis also causes inflammation when inflammatory mediators, molecules released by immune cells, invade the joints, resulting in a noticeable increase in heat. These processes are painful and lead to lameness of varying degrees.

On a smaller-sized joint, such as the pastern or coffin joint, these changes may be more difficult to see, but you may note a ‘thickening’ of the area. In the hocks, horses will develop what clinicians call a “boggy hock,” with a lot of fluid present.

As a first step to diagnosing arthritis, the veterinarian will perform a lameness exam to try to identify where the horse’s pain is coming from. This exam usually includes the following steps:

• Trotting the horse: We watch the horse trot and try to identify if the pain is in the front or hind limbs.

• Flexion test: We bend the suspected limb for a short period of time and then trot the horse again to identify lameness.

• Nerve blocks or joint blocks: We use regional anesthesia to methodically block portions of the horse’s limbs. The anesthesia drug will numb the source of pain. If the horse moves normally when the afflicted joint is numb, this can indicate where the pain is coming from.

• X-rays: Once the source of pain is identified, we take radiographs. This type of imaging typically allows us to diagnose arthritis 99 per cent of the time.

• Bone scan: If we are unable to detect changes radiographically, the next step could be nuclear scintigraphy (a bone scan). But because of the higher cost of this imaging modality, we will sometimes recommend moving directly to treatment.

What is arthritis?

Osteoarthritis, more commonly referred to as arthritis, is a progressive, inflammatory disease that causes pain and stiffness in the joints. It causes cartilage – the hard, slippery tissue that covers the ends of bones where they form a joint – to break down. In horses, it has basically the same outcome as it does in humans. What we see is pain and limited motion in the affected joint, leading to deterioration of the horse’s performance and overall health over time.

It is most commonly seen in the hock, fetlock, pastern and coffin joints. The area in which arthritis develops often depends on what the horse does for a living; in reining horses, for example, it is more commonly found in the hocks.

It is thought that arthritis is, in part, brought on by age as well as other factors that would predispose a horse to the condition, such as strenuous activity, injury or a heavy training regimen, that cause wear and tear on the cartilage. Commonly, horses that are worked hard at a young age will begin to exhibit radiographic signs of arthritis due to cartilage injury when veterinarians examine them for lameness. That said, every horse is susceptible to arthritis, even a backyard horse that hasn’t been ridden for years. It’s like what happens with humans – age catches up with them. You might see a horse that hasn’t been worked hard for a living, but then, as they get older, they start to show some joint pain and get stiff, which leads to arthritis.

How can it be treated and managed?

Rest is the easiest and cheapest option for managing arthritis. If the horse is rested, some of the pain will go away, but he will continue to exhibit lameness when the affected area is physically stressed. In obese horses, weight loss is also recommended.

To manage a horse diagnosed with arthritis, it is advisable to cut back on how much you work him. Also, be aware that your horse might exhibit some pain before and after riding. Consider giving him some phenylbutazone (bute) before a ride and afterwards for a day or two. Make sure to let the horse rest between rides.

Some people use joint supplements to help maintain their arthritic horse. One commonly used supplement is polysulfated glycosaminoglycan (Adequan®), which is administered intramuscularly over a course of 28 days. Some studies have shown improvement in horses with administration of this drug. Popular oral supplements are products that contain chondroitin sulphate, glucosamine or hyaluronan, or a combination of these components. Unfortunately, there are no good, controlled equine clinical studies to support whether these oral products significantly improve arthritis in horses.

The next step, and one of the most common treatments for arthritis, is to inject the horse’s inflamed joints with corticosteroids. These steroid drugs reduce inflammation and pain within the joint so the horse can return to performing. The downside is that no matter which corticosteroid you use, you have a limited window of efficacy. The steroid will wear off and will need to be repeated.

Performance horses are almost like NASCAR race cars – during competitions, you see the pit crews doing lube changes, oil changes and wheel changes to the vehicles. The same thing happens with performance horses. Many of them, especially if they’re competing on a circuit, will be on a course of steroids. If a horse is diagnosed with arthritis in the hock, for example, the veterinarian will go ahead and inject steroids into the hock joint, and the horse will perform great for about four months. If and when the horse returns to the clinic, more radiographs will be taken to assess the changes, and then, typically, he will be given another steroid injection, along with hyaluronic acid (HA) to lubricate the joint. This course of treatment has its limits, however, due to the progressive nature of the disease.

One treatment that was researched and developed at the Western College of Veterinary Medicine (WCVM) is the practice of injecting ethyl alcohol into a horse’s hocks to reduce pain and encourage fusion of the joint. If the joint fuses, thereby eliminating movement between bones in the joint, the pain goes away. This therapy has proven successful in treating arthritis of the hocks. (See page 12 for a look at a joint that has fused due to degenerative joint disease.)

The next step to consider is surgical fusion of the arthritic joint. Veterinary surgeons can use a drilling technique across the joint to encourage joint fusion. Once it fuses, the horse can go back to normal performance. The downside with this surgery is that performance horses are routinely out of competition for at least a year, and only about 60 per cent of equine patients do well after the surgery.

The pastern is the joint in which surgery has had the best success. Surgery techniques have evolved from the insertion of a simple screw, to a procedure known as pastern arthrodesis, in which the surgeon places a plate and a screw into the joint. Following surgery, the horse is in a cast for up to a month. Once the cast comes off, the horse needs time and rest to allow the tissues to heal and ensure the implants stay in place, and the joint starts to fuse. The horse might be out for 10 months, but can normally go back to his normal performance level.

If owners want to go further with treatment, they could consider regenerative medicine. Different treatments include platelet rich plasma (PRP) therapy or interleukin-1 receptor antagonist protein (IRAP) injections. This type of therapy does not stop the disease. Rather, it is supportive therapy to help get the horse through the pain process and to try and return him to performance. Right now, there are mixed opinions about PRP and IRAP therapies in the literature, but there’s nothing relevant to say we’ve discovered the miracle treatment for arthritis.

In terms of new or experimental therapies, there is some recent evidence that extracorporeal shock wave therapy may be useful in the treatment of arthritis in horses. More experimental studies and clinical trials are needed, however, to see if shock wave therapy can be recommended as an optimal treatment. Horse owners are advised to use caution and consult their veterinarians before attempting any new treatments.

Is arthritis preventable?

Chances are that as your horse ages, he will experience some arthritis. As mentioned, the amount and degree of work a horse partakes in during his lifetime will determine how soon and how quickly the disease advances. A careful conditioning program throughout his life can help maintain his movement and comfort and prolong his career.