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Conquering Arthritis
Process of Inflammation in Horse Osteoarthritis
By Diane Ursu

My senior horse ended her days in our pasture at the age of 25. During her dying days, she would eat when we were there as if she were trying to make us feel better about her condition. The minute we looked the other way, she would stop eating. She would continue to do the little things we wanted her to do until her heart failed. It was ironic that this was the fate of a horse that had a lot of heart.

An Arthritic Horse Could Not Be Stopped

It wasn't those last days that showed her dedication to us. No, it was the last ten years. She lived with the pain of movement and began to creak and pop in her later years. It originated in her hocks and eventually worked its way to her stifles and shoulders. Yet, she never failed to jump, run, or even spin on her haunches. When I took her to her first and only USDF (United States Dressage Federation) endorsed show, it was the best ride we ever had in our 14 years together. She even took second place in Training Level Test 1 and fourth in Training Level test 4!

We were determined to get the most out of life in spite of the arthritis that was slowly taking over her joints. I firmly believed that arthritis was not the end of the world for my horse, and I knew that retiring her would only make the condition worse.

The Process of Inflammation in Horse Osteoarthritis

Arthritis is a painful, degenerative joint disease that affects many senior horses. It is the result of chronic inflammation. To understand how arthritis is related to inflammation, it is important to first understand the process of inflammation.

When an area is injured or infected, chemicals from injured tissues stimulate pain receptors which then start an impulse to the central nervous system (CNS). The brain processes the impulse and recognizes that there is a problem in that area, so it sends impulses to begin the immune response. The brain also creates the sensation of pain to prevent usage of the injured area so further damage will not happen.

Blood vessels dilate to increase blood flow to the injured area. The increased blood flow causes redness, swelling, and heat. The heat is caused not only by increased blood flow, but because blood from deeper, warmer tissues is delivered to the injured site.

Capillaries are the smallest blood vessels connecting arterioles (small arteries) with venules (small veins). There are gaps in the capillary walls that allow for the exchange of nutrients and wastes, and oxygen and carbon dioxide. During inflammation, the capillaries dilate, increasing the size of the gaps in their walls. This allows for white blood cells to leave the capillaries and move to the injured area where they are attracted by a chemical released by damaged tissues.

When the white blood cells (phagocytes) arrive, they begin eating everything in the area (phagocytosis). Think of it like dusting a table. Before you can dust, you first have to remove everything off of the table, like remote controls, books, vases, etc. When the table is cleared off, then you will begin to put everything where it belongs. The same thing happens in the body.

For example, when you cut yourself, your body goes through all of the above steps. It then begins to either regenerate by creating more cells and making the area like it was before, or it repairs the area by replacing the injured skin with scar tissue. This is where the process of inflammation is different in the joints.

As stated before, the phagocytes arrive in the injured area and eat everything, including cartilage. Cartilage is the cushioning at the ends of bones in joints that keeps the bones from grinding together. Since there is no blood flow in the joint capsule (the joint capsule consists of the ends of the bones, the cartilage, and serous fluid in and around the area), and chondrocytes (cartilage cells) reproduce slowly, cartilage is not easily replaced. Therefore, after an inflammatory response in a joint, and the phagocytes have cleaned up the area (including some of the cartilage), there is less cartilage in the joint than there was before the injury.

Sometimes, the lessened amount of cartilage may cause some pain. The destruction of cartilage from the immune response will also signal the brain that there is more damage in the joint. This will trigger the immune response again, causing inflammation and its consequences. With osteoarthritis, this can become a continuous cycle.

The continuous cycle of inflammation of the joint causes the breakdown of cartilage that is known as osteoarthritis.

Decreasing the Odds - Causes of Horse Osteoarthritis

While arthritis really cannot be prevented, there are some steps that can be taken to decrease your horse's chance of getting arthritis. The biggest risk factor of arthritis is age, or time. Aging may lead to the wear-and-tear of joints and can become a bigger problem for some, leading to arthritis.

Increased weight is a significant and common risk factor for people, and can have the same affect on horses. The joints are only made for so much weight, and that is a healthy weight. Obese horses may be more likely to develop arthritis than horses of a healthy weight. The excess weight adds more stress to joints and can lead to wear-and-tear and inflammation.

Knowing that wear-and-tear can lead to arthritis may lead you to think that it is best to keep the horse still when it comes to joint health; however, this couldn't be further from the truth. Inactivity is also a large risk factor for arthritis. Movement promotes the production of serous fluid in the joints, thus causing more lubrication. This extra lubrication leads to lesser resistance within the joint, decreasing the chances of inflammation due to wear-and-tear.

As a kid in 4-H, I was always taught to warm up my horse before doing any serious work. It was important to walk the horse for at least 10 minutes to warm up its muscles and joints. What these 10 minutes actually do is trigger the need for more lubrication in the joints. The same thing is done in the muscles with blood.

Riding the Horse - Arthritis and the Warm-Up

I continued to show my horse well into her arthritic years partially because I was in denial that it would make that big of a difference. However, as the years went by, and the arthritis got worse, I realized just how important a warm-up was, and that the warm-up had to be longer in order to relieve the stiffness of her joints.

When riding an arthritic horse, it is important to walk the horse for the first 15 or 20 minutes. Let the horse start out at it's own pace and enjoy itself. After five or ten minutes, move the horse into a faster walk. It is important to do a working walk for about five or ten minutes to increase lubrication. Take another five or ten minutes and alternate trot-work with walking. After these first 20 to 30 minutes, it is safe to do a regular workout. After your workout, take the time to do a typical cool-down. As always, pay attention to how your horse feels by noticing any limping.

Horse Joint Supplements

Just as people take aspirin, ibuprofen, and other anti-inflammatories, your arthritic horse should be on them as well. When I was treating my horse for arthritis, I gave her joint supplements for horses such as glucosamine, and an anti-inflammatory pain medication called bute (phenylbutazone) on an as-needed basis. A good rule of thumb for determining whether or not your horse needs an anti-inflammatory is that pain is often accompanied by some kind of inflammation. Talk with your vet to determine the right course of action for your arthritic horse.

How Does My Horse Feel?

I learned that riding my horse after an adequate warm-up, keeping her at a healthy weight, and giving her an anti-inflammatory helped to keep her joints healthy throughout her life. It was evident that the horse joint supplements worked. I'll never forget that amazing performance my horse gave at her only USDF dressage show.

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