Platelet Dose, Concentration, and Injectate Volume in Platelet-Rich Plasma Therapy: An Evidence-Informed Review of Large-Joint Osteoarthritis

Background/Objectives: Platelet-rich plasma (PRP) preparations vary widely, and most studies report concentration rather than absolute platelet dose, limiting cross-study comparison. This review provides an evidence-informed synthesis of platelet dose, concentration, and injectate volume in knee, hip, and glenohumeral osteoarthritis (OA). Methods: A PubMed-based narrative review included 26 primary studies (16 knee, nine hip, and one glenohumeral); systematic reviews provided context. Dose was classified as directly reported, calculated from measured product characteristics, nominally estimated, or assumption-dependent/unverifiable. Assumption-dependent values were excluded from numerical ranges. Randomized trials were assessed with the Cochrane Risk of Bias 2 tool. Results: Knee OA provided the strongest dose-related evidence. Reported, calculated, or aggregate study-level dose estimates ranged from approximately 2.5 to 13.7 billion platelets per injection, with findings suggesting a dose-related signal at approximately 5 billion platelets or greater. In hip OA, measured protocols associated with clinical improvement delivered approximately 6.2–7.0 billion platelets per injection. Glenohumeral evidence was limited to one trial. However, overall, the available evidence did not establish validated minimum or optimal dose thresholds. Conclusions: In knee OA, the available literature shows a dose-related signal at approximately 5 billion platelets or greater per injection, while hip studies report measured protocols around 6–7 billion platelets per injection. These findings are descriptive rather than prescriptive and do not establish clinical dosing thresholds or recommendations. Glenohumeral evidence remains insufficient for dose-specific conclusions.