Veterinarians often use PRP to treat joint disease in horses. | Adobe StockVeterinarians often use platelet-rich plasma (PRP) to treat equine joint disease, but the lack of standardized preparation methods has limited their ability to accurately assess its clinical efficacy. Without standardization, rigorous research to conclusively determine PRPs therapeutic value in equine joint treatments cannot be performed, said Omar Maher, DVM, Dipl. ACVS, ACVSMR, during the 2025 American Association of Equine Practitioners Convention, held Dec. 6-10 in Denver, Colorado.Maher, the founder of Atlantic Equine Services, with locations in Wellington, Florida, and Dover, New Hampshire, presented on behalf of his co-author, Philippe Benoit, DVM, MS, Dipl. ACVSMR. In their Proceedings paper they emphasized that the lack of PRP preparation consistency ultimately limits the clinical utility of what can be a valuable orthobiologic for managing equine joint disease.Maher explained that veterinarians currently produce PRP either by centrifugation or filtration of a horses blood sample. The resulting plasma suspension contains platelets, variable numbers of white (leukocytes) and red blood cells, and plasma proteins. This product is rich in growth factors, including transforming growth factor, platelet-derived growth factor, and others that researchers report might support tissue healing and modulation of inflammation.Preparing PRP for HorsesWe are in a primitive stage of understanding PRP, said Maher. There is no standardization in terms of platelet concentration or injection method. And the available studies dont typically describe what kind of PRP they are using or whether it was even PRP at all because the platelet concentration was not measured.Samples often differ in color, which reflects differences in their cellular composition. Its difficult to expect that each of these PRPs will do the same job, he added.Maher outlined several key questions practitioners should consider when preparing PRP:Do we want a leukocyte-rich or leukocyte-poor PRP (in some conditions more white blood cells might be desirable, whereas fewer are better with others)?What platelet concentration and dose should we be using?How do we harvest and store the PRP?What delivery method should we use (needle size, number of injections, dosing interval)?How do we take patient variability into consideration?What Do Researchers Know About PRP in Horses?Maher highlighted work conducted by the GRIIP (International Research Group on Platelet Injections), which reviews literature on PRP use for human knee osteoarthritis (OA) annually.That group has a preference for low leukocytes, using between 4 and 8 milliliters in the knee (which is smaller than a horses stifle), having a platelet concentration less than five times the blood concentration, and typically using PRP in patients with mild to moderate OA, he said.The GRIIP also recommends patients not receive non-steroidal anti-inflammatory drugs (NSAIDs) at the time of treatment and that clinicians administer one to three injections. They advise against co-administering PRP with local anesthetics, because locals appear toxic to platelets. They also recommend using ultrasound guidance whenever possible to reduce the risk of painful extra-articular injections, avoiding concurrent use of corticosteroids, and injecting PRP on the same day it is prepared to potentially improve the outcome following injections.PRP Recommendations for Equine PractitionersBased on these human-medicine guidelines, Maher advised collecting blood samples for PRP preparation prior to exercise and while the horse is not on any medications. Veterinarians should perform a traditional complete blood cell count (CBC) prior to processing to establish baseline platelet, white blood cell, and red blood cell counts. After PRP preparation they should analyze the final product again to determine platelet concentration.As for dose and volume, for a coffin joint, we recommend 1 billion platelets in 3 milliliters, but for a stifle we recommend 4 billion platelets in 8 milliliters, said Maher. These numbers were chosen based on experience and seem to be effective with minimal amount of flare. (Joint flare, also called reactive synovitis, can occur after intra-articular injection.)Maher and Benoit gained much of this experience in Wellington, Florida, where they treated 450 horses from 21 veterinary practices. They found both baseline platelet counts and PRP platelet concentrations varied significantly among individual horses. Some of the PRP was too dilute, and we couldnt use it, Maher said. This shows how important it is to measure the product, so we know what were injecting.Take-Home MessageBased on their available data and clinical experience, Maher and Benoit currently recommend using low-leukocyte PRP preparations, standardizing platelet numbers and injection volumes across patients, and using ultrasound guidance for deeper joints. They also advise against sedating horses prior to blood collection for PRP and recommend avoiding the use of corticosteroids and long-term NSAIDs in conjunction with PRP therapy.