Efficacy of Platelet-Rich Plasma Injections in Knee Osteoarthritis: A Systematic Review and Meta-Analysis.

Abstract

The study was conducted to evaluate the safety and effectiveness of platelet-rich plasma (PRP) injections for knee osteoarthritis. A systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Searches were performed in PubMed, Scopus, Web of Science, and the Cochrane Database for studies published between January 2015 and June 2025. Only randomized controlled trials (RCTs) published in the English language were included, while reviews, case reports, and non-randomized studies were excluded. Six high-quality RCTs were identified, including a total of 1,162 patients with mild-to-moderate knee osteoarthritis. PRP injections were compared with hyaluronic acid, corticosteroid injections, or placebo. Pain and function were assessed using standardized tools such as the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), the International Knee Documentation Committee (IKDC) score, the Knee Injury and Osteoarthritis Outcome Score, and the Visual Analog Scale. Significant improvements with PRP were observed at 6 and 12 months. The WOMAC pain score was reduced by an average of -8.5 points, and the IKDC score increased by +6.2 points. Both results were statistically significant. Moderate variability was found between studies, but sensitivity analyses confirmed stability of the results. Subgroup analysis did not show consistent differences between leukocyte-rich PRP and leukocyte-poor PRP. Reported side effects were minor and self-limiting. Overall, PRP demonstrated significant improvements at 6 and 12 months. Pooled analysis indicated moderate pain reduction (standardized mean difference (SMD) = -0.32, 95% confidence interval (CI) = -0.48 to -0.15; I² = 46%) and functional improvement (SMD = -0.28, 95% CI = -0.44 to -0.12; I² = 52%) compared with control groups. However, long-term structural improvement was not demonstrated. Larger trials are still needed to confirm benefits, optimize preparation methods, and assess cost-effectiveness.