PRP Injections for the Treatment of Knee Osteoarthritis: The Improvement Is Clinically Significant and Influenced by Platelet Concentration: A Meta-analysis of Randomized Controlled Trials

Platelet-rich plasma (PRP) has emerged as a promising therapeutic intervention for knee osteoarthritis (OA), attracting substantial clinical and research attention. However, the clinical relevance of the treatment benefit remains controversial. PURPOSE: To evaluate the effectiveness of PRP compared with placebo in patients with knee OA in terms of minimal clinically important difference (MCID) and to investigate the possible influence of platelet concentration on the clinical outcome. STUDY DESIGN: Meta-analysis. Level of evidence 1.

The search was conducted on 5 databases (PubMed, Cochrane Library, Scopus, Embase, Web of Science) using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Inclusion criteria were randomized controlled trials comparing PRP and placebo injections to treat knee OA, written in the English language, with no time limitation. The effects were quantified at 1-, 3-, 6-, and 12-month follow-up points. Visual analog scale (VAS) for pain and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores were used, with subanalyses based on platelet concentration performed using a 1,000,000 ± 20% platelets/µL cutoff. The MCID values (VAS, 1.37; WOMAC, 6.4) were used to interpret clinical improvement. The articles' quality was assessed using the Revised Tool for Risk of Bias in Randomized Trials and the Grading of Recommendations Assessment, Development and Evaluation guidelines.