Adipose- and bone marrow-derived stromal cells reduce pain in patients with knee osteoarthritis but do not substantially improve knee functionality: an updated systematic review and meta-analysis.

Purpose: To perform a systematic review and meta-analysis of randomized and comparative studies comparing mesenchymal stromal cells other orthobiological injections for patients with knee osteoarthritis.

Methods: Systematic review of Medline, Embase, Scopus, and Google Scholar, including all level 1-3 from 2014 to 2024. Validated scores (VAS, KOOS, Lysholm, IKDC) were included as outcome measures. Risk of bias was assessed using the Cochrane Collaboration's tools. The GRADE system was used to assess the quality of the body of evidence and the modified Coleman Methodology score was used to assess study quality. Heterogeneity was assessed using χ² and I² statistics.

Results: Ten studies were included; all published in English between 2019 and 2023, encompassing a total of 563 cases (281 treated with MSCs and 282 with other biologics). Two studies had a high risk of bias, one had some bias, and seven had a low risk of bias. Publication bias was detected (Egger's test 3.26447; p = 0.007). The pooled estimates revealed significant differences favoring MSCs for VAS scores at 3, 6, and 12 months. For KOOS pain and symptoms, significant differences were observed at 3 and 6 months.

Conclusion: The results of this meta-analysis demonstrated a significant effect of adipose and bone marrow-derived stromal cell injections on pain reduction at all assessed time points, and showed superiority over other non-surgical treatment options. These differences were not reflected in clinical and functional outcomes, indicating that the observed reduction in pain did not correspond to substantial improvements in knee functionality.