Comparative efficacy of stem cell-based therapies versus platelet-rich plasma for knee osteoarthritis: A systematic review and narrative synthesis

Abstract

To systematically review clinical, functional, and structural outcomes of stem cell-based therapies compared with platelet-rich plasma (PRP) for knee osteoarthritis (OA). A systematic search of PubMed, ScienceDirect, and Google Scholar was conducted for studies published from January 01, 2021, to March 31, 2026, directly comparing stem cell-based therapies with PRP for knee OA. Outcomes included pain scores, WOMAC, knee injury and osteoarthritis outcome score, International Knee Documentation Committee score, and magnetic resonance imaging findings. Six studies involving 433 patients met the inclusion criteria, including three randomized controlled trials, two retrospective comparative studies, and one multicenter randomized study. Interventions included bone marrow aspirate concentrate, microfragmented adipose tissue, and expanded adipose-derived stromal cells compared with different PRP formulations. High-quality randomized trials showed no significant clinical superiority of stem cell-based therapies over PRP at 6–24 months, with both groups demonstrating sustained improvements. Retrospective studies suggested greater improvement with some cell-based products, but these findings were limited by selection bias, small sample size, and heterogeneity. Current evidence does not demonstrate consistent superiority of stem cell-based therapies over PRP for knee OA. Both treatments may improve pain and function, but structural benefit remains unproven. Larger standardized randomized trials with longer follow-up are required.