## 4 Discussion
This underscores the need for standardized protocols and further research to better understand the factors that contribute to the success of PRP treatments for equine musculoskeletal injuries. In addition, future studies should investigate the role of patient-specific factors such as age, breed, and injury severity in determining the optimal PRP formulation and treatment protocol. Half of the studies included in this review did not report whether PRP was activated before use or specify the activation method. However, good clinical and experimental outcomes were observed in studies where PRP was either not activated or activated using calcium chloride [18; 39; 43; 52; 53] or bovine thrombin [17]. These findings suggest that the activation of PRP may not be essential to enhance its therapeutic effects when injected into injured tendons and ligaments. However, the data from this systematic review do not provide sufficient evidence to draw definitive conclusions regarding the necessity of using activators for PRP in the treatment of equine tendon and ligament disorders. In particular, the activators commonly used in these studies, such as calcium chloride and bovine thrombin, have been associated with potential drawbacks, including crystal deposition (calcium chloride) and inflammatory reactions (bovine thrombin) in treated tissues [58; 59; 60]. This raises concerns about their suitability for clinical use. In contrast, calcium gluconate, which does not precipitate into crystalline forms in PRP clos, has been proposed as a more favorable alternative [58]. Further research is needed to evaluate the efficacy and safety of various activation methods, including non-activated PRP, to optimize treatment protocols for equine musculoskeletal injuries. In addition, future studies should explore alternative activation methods, such as the use of autologous thrombin or mechanical activation, to minimize potential adverse effects. The dosing regimen for PRP varied widely across studies, with injection volumes ranging from 1 mL to 12 mL per treatment. The majority of studies used a single intralesional injection, while one study used multiple injections administered at 2-week intervals, particularly for chronic injuries [18]. The volume of PRP administered was often adjusted based on the size and severity of the lesion, suggesting a tailored approach to treatment. Although single injections have demonstrated efficacy in many cases, repeated administrations may provide an additional benefit for more severe or chronic conditions [18; 38]. However, the lack of standardized dosing protocols highlights the need for further research to establish evidence-based guidelines. Notably, in all case series and randomized clinical trials, PRP administration was combined with controlled exercise protocols implemented to enhance tissue adaptation and promote functional recovery. This combination underscores the importance of integrating PRP therapy with rehabilitation strategies to optimize the clinical outcomes of equine tendon and ligament injuries. Future research should also investigate the optimal timing and frequency of PRP injections, especially in chronic or recurrent injuries, to maximize the therapeutic benefits. Short-term outcomes (1-3 months) showed that PRP treatment was associated with significant improvements in lameness scores and ultrasound appearance in most clinical studies [37; 38; 42; 43; 45]. Medium-term outcomes (3.1-11.9 months) showed continued improvements in tissue healing and functional recovery, with many horses returning to previous levels of activity [17; 38; 41]. Long-term outcomes (1 year or more) were more variable, with some studies reporting sustained improvements [18; 37; 39; 40; 42] and others noting a decline in performance, particularly in horses with chronic cases [17; 40; 42; 44]. Overall, PRP appears to be effective at promoting short- and medium-term recovery, but its long-term efficacy may depend on factors such as the injury severity and concurrent therapies.