The Efficacy of Intra-Articular Mesenchymal Stem Cell Injection for Knee Osteoarthritis: A Systematic Review and Meta-Analysis

Abstract

Introduction: Knee osteoarthritis (OA) is a leading cause of disability, characterized by cartilage degradation and inflammation. Mesenchymal stem cells (MSCs) have emerged as a promising regenerative therapy due to their chondrogenic and anti-inflammatory properties. This review synthesizes the current evidence on the efficacy and safety of intra-articular MSC injections for knee OA.

Methods: A systematic search was conducted in PubMed, Embase, and Cochrane Library for randomized controlled trials (RCTs) published up to December 2024. Studies comparing intra-articular MSC injections with placebo or conventional treatments (e.g., hyaluronic acid) were included. Primary outcomes were pain reduction (Visual Analogue Scale - VAS) and functional improvement (Western Ontario and McMaster Universities Osteoarthritis Index - WOMAC).

Results: Twenty-five RCTs involving 1,520 patients were included. The meta-analysis revealed that MSC injections led to a statistically significant reduction in VAS pain scores (Mean Difference: -2.1; 95% CI: -2.8 to -1.4; p < 0.001) and improvement in WOMAC function scores compared to controls at 12-month follow-up. Cartilage thickness improvement was noted in several studies via MRI, though methodologies varied. No severe adverse events directly related to the therapy were reported.

Discussion: The findings suggest that MSC therapy is a safe and effective treatment for symptomatic relief and functional improvement in knee OA. The therapeutic benefit is likely mediated through paracrine anti-inflammatory and trophic effects rather than direct cartilage regeneration. However, heterogeneity in cell sources (bone marrow, adipose), dosage, and preparation methods across studies warrants cautious interpretation.

Conclusion: Intra-articular MSC injection is a promising therapeutic strategy for knee osteoarthritis, offering significant clinical benefits over conventional treatments. Standardization of protocols and further long-term studies are necessary to establish its place in clinical practice.