Introduction: Mesenchymal stem cells (MSCs) have gained popularity for articular cartilage repair. However, efficacy of intra-articular MSCs in osteoarthritis remains unclear. In the setting of a meta-analysis of randomized controlled trials (RCTs), we aimed to investigate the efficacy of intra-articular MSCs on clinical outcomes and cartilage repair in patients with knee osteoarthritis.

Materials and methods: PubMed, EMBASE, Cochrane Library, CINAHL, and Scopus were searched from inception to March 31, 2017. This study included RCTs using cell population containing MSCs for treatment of knee osteoarthritis. The quality was assessed by Cochrane Collaboration`s risk of bias tool. For meta-analysis, data on clinical outcomes measured by visual analog scale (VAS), Lysholm score, WOMAC and data on cartilage repair measured by MOCART and WORMS were extracted. In studies with several cell concentrations, outcomes of recommended concentration were used mainly to ensure robustness.

Results: A total of five RCTs (220 patients) were included. Two studies were deemed to have low risk of bias. In pooled analysis, there was significant difference in VAS score (mean difference [MD], - 9.2; 95% CI: - 17.21, - 1.20) and Lysholm score (MD, 8.70; 95% CI 0.06, 17.34), but not WOMAC (MD, - 7.44; 95% CI - 20.38, 5.50). In cumulative functional analysis using Lysholm score and WOMAC in recommended concentration, there was a significant improvement (standard mean difference [SMD], 0.53; 95% CI 0.13, 0.94) after treatment. In cartilage repair assessed by MRI, there was no significant difference (SMD, 0.53; 95% CI- 0.28, 1.34).

Conclusions: This meta-analysis demonstrated that intra-articular MSCs have a limited evidence in pain relief and functional improvement in knee osteoarthritis. While MSCs may result in favorable clinical outcomes with a recommended concentration, use of concomitant treatment should be considered. In addition, current evidence does not support the use of intra-articular MSCs for improving cartilage repair in knee osteoarthritis.

Level of evidence: Systematic review of Level-II studies.