Hyaluronic Acid and Other Treatments for Carpal Disease in Horses

Mild osteoarthritis in the carpal joint, or knee, limits a horse’s ability to perform at the top of its game. While several treatment options are currently used, a gold standard has yet to be identified. With this in mind, three treatments for naturally occurring carpal disease in Thoroughbreds were compared for efficacy: triamcinolone, hyaluronic acid, and 2.5% polyacrylamide hydrogel (PAAG).^* The greatest improvement in lameness occurred in horses treated with PAAG, but hyaluronic acid also performed well, better than triamcinolone.

The horses included in the study were two to six years old and actively involved in training. All had naturally occurring carpal disease isolated to the middle carpal joint based on lameness, joint effusion, and flexion tests. X-rays confirmed the absence of fractures or bone fragments. Horses were randomly assigned to receive one of three treatments that were administered directly into the affected joint:

• 50 mg (2 mL) 2.5% PAAG;
• 12 mg (2 mL) triamcinolone; or
• 20 mg (2 mL) hyaluronic acid. These horses were also administered two intravenous injections of hyaluronic acid (40 mg, 4 mL) at weekly intervals.

Researchers re-evaluated the horses two, four, and six weeks after treatment. Results were consistent over the course of the study, with significantly more sound horses in the PAAG group compared to either triamcinolone- or hyaluronic acid-treated horses. Specifically, at the end of the six-week study, 83% of the PAAG-treated joints were free from lameness compared to 27% and 40% of the joints in the triamcinolone and hyaluronic acid groups, respectively.

“An interesting finding in this study was the low success rate of triamcinolone treatment, a commonly used corticosteroid in equine practice,” said Catherine Whitehouse, M.S., a nutrition advisor for Kentucky Equine Research.

Researchers did not expect hyaluronic acid to outperform triamcinolone. They suggested that hyaluronic acid may have been administered early enough in the course of inflammation that it had time to effectively alter the course of the natural disease process.

“Hyaluronic acid may act through biochemical and genetic modifications beyond its lubrication and shock-absorption properties,” explained Whitehouse.

She added, “Large, rapidly growing horses and young horses in training are great candidates for proactive oral supplementation with hyaluronic acid, as it supports the maintenance of healthy joints. Synovate HA, a high-molecular weight product developed by Kentucky Equine Research, has positively affected stride length and frequency in exercising horses.”

In sum, this study provides veterinarians with important information regarding treatment options for the early management of middle carpal joint lameness in active racehorses.

*de Clifford, L.T., J.N. Lowe, C.D. McKellar, C. McGowan, and F. David. 2021. A double-blinded positive control study comparing the relative efficacy of 2.5% polyacrylamide hydrogel (PAAG) against triamcinolone acetonide (TA) and sodium hyaluronate (HA) in the management of middle carpal joint lameness in racing Thoroughbreds. Journal of Equine Veterinary Science 107:103780.