Arthritis in the Performance Horse

Arthritis causes considerable pain in your horse, and understanding the disease cycle is necessary in order to prevent further damage from occurring. "One-third of all lameness is due to arthritis or soft tissue trauma," said Rhonda Rathgeber, DVM, PhD, of Hagyard Equine Medical Institute in Lexington, Ky. She spoke at an educational event held April 30 during the Rolex Kentucky Three-Day Event. "Joint disease occurs from repeated use for training and performance. It is a vicious cycle of damage."

Arthritis Overview

There are three types of joints in the horse’s body: Fibrous (in the skull), cartilaginous (between the sternum and ribs), and synovial (where two or more bones join to allow movement). Joint disease most often occurs in the synovial joints because of the wear and tear that occurs in performance horses from heavy training and exercise.

"Synovial joints consists of external supportive structures, such as skin, muscles, tendons, and ligaments, which are important to keep the joint in line and contribute to joint health," said Rathgeber. "Damage to them can lead to joint injury.

"When damage occurs to the support structures, there is a change in the normal movement of the horse," she noted. "There are a lot of nerves in the joint capsule, and a lot of pain can occur when there is damage to the joint capsule."

Signs of joint damage include heat, pain, swelling around the joint capsule, and lameness. "The joint capsule encloses the entire joint and contains blood vessels, which are a nutrition source for the joint and a source of synovial fluid," said Rathgeber. The joint capsule provides joint stability, maintains a range of motion, and creates hyaluronic acid and synovial fluid (the fluid that lubricates the joint and is mainly composed of hyaluronic acid).

"Hyaluronic acid is a big molecule which creates the thickness of the joint fluid," commented Rathgeber. "A change in the hylauronic acid changes the way the joint moves."

Force from movement is transmitted evenly across the articular cartilage. "Articular cartilage is like a Tempurpedic pad on the end of each joint. The cartilage is thicker on the end of the joint to absorb force," said Rathgeber. "It is nourished by the synovial fluid, but has no blood supply so it cannot heal."

Once damage occurs to articular cartilage, it cannot be reversed. "Normal joint nutrition occurs as the articular cartilage is compressed, new joint fluid comes in as cartilage is released (uncompressed) and sucks in fluid like a sponge," noted Rathgeber. "Freedom of motion is necessary for normal joint nutrition and metabolism. Exercise is needed to keep joints healthy."

Subchondral bone is the actual shock absorber in the joint. This bone is in every joint and is beneath the articular cartilage. "The subchondral bone is constantly is a state of remodeling and repair. If the damage exceeds the rate of repair, then damage to the subchondral bone is the end-stage process, and arthritis occurs," noted Rathgeber.

Too much heavy exercise and force on the joints leads to inflammation. "Inflammation is our friend because it heals, but it can get out of hand, which is when the damage occurs," said Rathgeber.

As inflammation increases, the synovial fluid becomes less viscous (watery), inflammatory mediators are released (molecules released by immune cells that try to clean up small pieces of cartilage that are floating in the joint), cartilage cell function decreases, and articular damage occurs because the normal joint repair process cannot keep up with the damage. "Lameness is the last stage of the disease," she said.

"As cells and enzymes damage the cartilage, the cartilage begins to resemble the old foamy saddle pad that has been washed too many times and is now lumpy," said Rathgeber. Shock is no longer evenly transmitted, leading to bone damage.

Treatments for Arthritis

"No drug treatment can lead to the replacement of lost cartilage," explained Rathgeber. Once joint damage has occurred, there is no turning back. However, horse owners must take steps to keep further damage from happening.

"The most prescribed treatment for arthritis is rest," said Rathgeber. While stall rest is useful, light exercise and movement is necessary for joint health, so a recovery program that involves light exercise (such as hand-walking or supervised turnout) should be discussed with your veterinarian.

Physical therapy is also beneficial to horses, just as it is to humans. Rathgeber said types of physical therapy include cold hydrotherapy or ice for acute inflammation, heat for chronic inflammation, support wraps, liniments, poultices, hand walking, therapeutic laser and ultrasound, and passive flexion of joints.

There are many pharmaceutical options available that can help relieve pain in your horse and help prevent further damage from occurring. These include intramuscular, intravenous, and intra-articular injections, as well as oral and topical medications.
"Adequan, which is harvested from bovine trachea, reduces inflammation in the joint and stimulates production of hyaluronic acid within the joint," said Rathgeber. Peak levels of the drug occur in articular cartilage within 24-48 hours after injection; repeat injections need to be given every four days for one month, then as needed to maintain levels.

"Corticosteroids are the most potent treatment for relieving inflammation, which is the goal in treating joint disease," stated Rathgeber. She said steroids are best used when hyaluronic acid is administered in the joint simultaneously; inflammation is reduced, and the joint is lubricated. Rathgeber also stressed that the literature does not support the risk that putting steroids in the joint will cause damage.

"NSAIDs (such as Bute and banamine) are a short-term treatment that are very good and are easy to give," said Rathgeber. Although side effects of NSAIDs include potential toxicity, SURPASS, a new topical cream produced by IDEXX, works well with less potential for serious problems.

There are numerous oral joint supplements available to horse owners, but Rathgeber cautions using them as the sole treatment. "Oral joint supplements haven't been proven to work," she said. "Joint supplements don’t treat damage to the subchondral bone, but are thought to be a 'building block' for the proteins needed for joint repair. There is a place for them, but they shouldn't be used freely."

Other treatments that are emerging are synovial fluid with serum markers, gene therapy, articular cartilage repair, and stem cell therapy.

Rathgeber left horse owners with a simple take-home message: "Degenerative joint disease is a vicious cycle. Unless this cycle is disrupted, it will continue to degrade the joint."

About the Author

Marcella M. Reca Zipp, MS

Marcella Reca Zipp, M.S., is a former staff writer for The Horse. She is completing her doctorate in Environmental Education and researching adolescent relationships with horses and nature. She lives with her family, senior horse, and flock of chickens on an island in the Chain O'Lakes.

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