Types of Medication
Our experts say there are three main types of medication used to treat the hock through injection: hyaluronic acid, cortisone and IRAP therapy.
Hyaluronic acid—Of the three, hyaluronic acid is the most commonly used medication for joint therapy. Naturally occurring in the joints when administered orally or injected into the horse, it mainly provides lubrication to the joints, cushioning impact. Tanner prefers Hyvisc because it has a high molecular weight, offering greater viscosity that holds up longer in the joint.
“I believe hyaluronic acid results in the longest-term alleviation of pain in the joint, unless there is extensive arthritis associated with the joint,” Tanner said.
Harvey says hyaluronic acid possesses very little anti-inflammatory effects, but it helps to improve the health of the joint.
“Hyaluronic acid has the building blocks for the cartilage and the joint capsule to help improve the viscosity of the fluid,” Harvey said.
Cortisone—Injectible corticosteroids mimic the cortisol that naturally circulates in the body when secreted by the adrenal glands. Cortisone steroids such as intermediate-acting triamcinolone and long-acting depo-medrol work to reduce inflammation in the joint, therefore returning the joint to a quiescent—without troublesome symptoms—state. Tanner says he uses cortisone on horses who have osteoarthritis. He says cortisone products are highly effective, but when repeated too frequently—particularly the longer-acting products—they can accelerate wear on the cartilage. He typically uses Vetalog and Betazone.
“[Cortisone injections] are very strong—it’s the strongest thing you put in a joint to alleviate soreness, but the downside is that you can’t use it too frequently because it can have a softening effect on the cartilage and can increase the wear on the cartilage,” Tanner said.
Harvey usually uses a compound of a corticosteroid, hyaluronic acid and an antibiotic to reduce inflammation, nourish the joint and reduce chances of infection from the needle entering the joint. The mixture is adjusted to suit the horse’s particular needs, and to address the amount of pathology in the joint.
“We do use cortisone in young horses to reduce inflammation,” Harvey said. “But they get a smaller amount than an older horse, with a greater amount of hyaluronic acid if they have more joint space. Horses with severe osteoarthritis are going to get less hyaluronic acid because there is less cartilage to nourish.”
IRAP therapy—IRAP stands for interleukin-1 receptor antagonist protein. It is a serum created from the horse’s own leukocytes—white blood cells, which are incubated for 24 hours, then centrifuged into a serum injected back into the horse, often at the hock joint. It acts as a natural anti-inflammatory. IRAP has been on the market for a couple of years, and it’s shown to be a good option for some horses. Tanner feels IRAP can help heal the joint, rather than only treating inflammation.
“The benefits are it is made from the horse’s own product, so it’s very kind to the joint itself, especially for horses who have to be managed long-term,” Tanner said.
The downside to IRAP is the cost—it is more expensive than the other therapies available for hocks, and Tanner says the effects don’t last as long.
“It’s very kind to the joints, it does a good job, but you’re going to have to treat more frequently with that product,” Tanner said.
Tanner often blends hyaluronic acid and IRAP products when treating hocks. He will also use IRAP in between conventional joint injections to spread out the need for the use of synthetic products.