by Kentucky Equine Research Staff
Veterinary researchers recently conducted a comprehensive review of 22 studies using platelet-rich plasma (PRP) to treat tendon and ligament injuries in horses.* These soft-tissue injuries are major contributors to lameness and result in substantial economic losses for both owners and trainers. Despite growing interest, limited controlled clinical data support the efficacy of PRP.
PRP is a type of orthobiologic therapy derived from the horse’s own blood. The blood sample is processed, usually by centrifugation, to create a concentrated suspension of live platelets and white blood cells. This mixture is then injected directly into the horse’s injured soft tissue, guided by ultrasound.
“After the PRP is injected, it transforms into a platelet-rich ‘gel’ that releases growth factors and anti-inflammatory mediators,” explained Catherine Whitehouse, M.S., a nutrition advisor for Kentucky Equine Research.
Those molecules then attract nearby stem cells and promote regenerative mechanisms that ultimately help repair and heal damaged tissues.
During the researchers’ review of the studies, they asked six questions that may help owners better understand PRP.
- Is PRP safe in horses?
Yes, across all 22 studies, no significant adverse effects were reported following PRP treatment.
- What is the most common way of producing PRP?
Across the 22 studies, fresh whole blood volumes collected from horses ranged from 15 mL to 300 mL, with most researchers using between 50 and 81 mL. The standard method for producing PRP involved a double-centrifugation protocol; however, alternative approaches were used, including single-centrifugation semi-automated kits and gravitational filtration systems.
- What is the optimal concentration of platelets?
This remains unknown. The platelet concentration in PRP in the studies ranged from 100 x 103 to 1,370 x 103 platelets/ìL. When reported (only nine of the 22 studies reported concentration), this value alternated between 1.3 to 8.7 times the concentration of platelets in whole blood.
- What “dose” of PRP should be injected and how often?
Veterinarians injected platelet-rich plasma directly into the lesions in all studies. The volumes varied dramatically, from 1 mL to 12 mL. Most studies used between 2 mL and 5 mL, and most adjusted based on the size of the lesion on ultrasound. Most studies used a single injection, but one study performed three injections into the same lesions at two-week intervals.
“Considering that the concentration of platelets varied markedly in each PRP preparation, the difference in injected volume further complicates the issue of decoding the optimal dose,” explained Whitehouse.
- What were the clinical outcomes?
Platelet-rich plasma yielded positive results in 18 of the 22 studies (86%), with researchers citing improvements in lameness, ultrasound appearance, and recovery times. However, researchers only reported positive results in two of the four randomized clinical trials when PRP was used as the only treatment. In the two randomized clinical trials with positive results, lameness scores decreased by 30% to 60% compared to 10% to 25% in the control groups.
The reviewers added, however, “PRP appears to be effective at promoting short- and medium-term recovery, but its long-term efficacy may depend on factors such as injury severity and concurrent therapies.”
- Can PRP be combined with other therapies?
Yes. All case series and clinical trials included in the review combined PRP with controlled exercise programs to enhance healing.
In some studies, PRP was also paired with mesenchymal stem cells or bone marrow aspirate concentrate. However, current data are insufficient to determine whether these combinations offer added benefit. Further research on combining PRP with other regenerative therapies, such as extracellular vesicles or gene therapy, is needed.
“Standardized reporting and methodological rigor of PRP studies should be improved to ensure reproducibility and facilitate evidence-based veterinary practice,” concluded the researchers.
“To support the horse’s musculoskeletal system, including soft-tissue structures and joints, offer oral joint health supplements,” recommended Whitehouse.
*Carmona, J.U., and C. López. 2025. Efficacy of platelet-rich plasma in the treatment of equine tendon and ligament injuries: A systematic review of clinical and experimental studies. Veterinary Science 12(4):382.
Reprinted courtesy of Kentucky Equine Research. Kentucky Equine Research is an international equine nutrition, research, and consultation company serving horse owners and the feed industry. Our goals are to advance the industry's knowledge of equine nutrition and exercise physiology, apply that knowledge to produce healthier, more athletic horses, and support the nutritional care of all horses throughout their lives. Learn more at Kentucky Equine Research.
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