Contextual effects of mesenchymal stem cell injections for knee osteoarthritis: systematic review and meta-analysis of randomized controlled trials

Relatively higher-quality human studies compared with other topics in this database, e.g. multiple RCTs or systematic reviews. This does not mean it is standard or approved care.

• Level A · Stronger Clinical Evidence
• Level B · Emerging clinical evidence with positive signals
• Level C · Early human research exploring benefits
• Level D · Scientific groundwork from lab and animal studies
• Emerging · Emerging topic under active research

Abstract (original English)

Purpose To quantify the proportion of the overall clinical improvement produced by intra-articular mesenchymal stem cell (MSC) injections for knee osteoarthritis (KOA) that is attributable to contextual (placebo-related) effects. Methods This PRISMA-compliant systematic review and meta-analysis (PROSPERO CRD420251026818) searched five databases (CENTRAL, Embase, MEDLINE, Web of Science and Scopus) to 24 March 2025. Randomized controlled trials enrolling adults with KOA that compared MSC injections with inert placebo were included. Primary outcome was change in pain intensity (VAS or WOMAC-pain); physical function was analysed secondarily. Two reviewers independently extracted data and assessed risk of bias. The proportion of the treatment effect attributable to contextual factors (PCE) was calculated as described by Tsutsumi et al. Pain and function outcomes at 6 and 12 months were pooled with inverse-variance random-effects meta-analysis, and evidence certainty was appraised using GRADE. Results Eight RCTs (467 patients) met the inclusion criteria. At 6 months, contextual factors accounted for approximately 63% of pain reduction and 61% of functional improvement, with low heterogeneity ( I 2 ≤ 8%). At 12 months, contextual factors explained ~50% of pain relief and ~66% of functional gains, again with very low heterogeneity ( I 2 = 0%). Certainty of evidence was rated low for b

Evidence level

Relatively higher-quality human studies compared with other topics in this database, e.g. multiple RCTs or systematic reviews. This does not mean it is standard or approved care.

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