Potential for Cartilage Restoration in Osteoarthritis Patients Through Intra-Articular Injection of Mesenchymal Stem Cells: An MRI-Based Morphological Evaluation of Repair Cartilage — A Narrative Review

Knee osteoarthritis (OA) is a progressive joint disease associated with pain and disability, and current treatments do not restore damaged articular cartilage. Intra-articular mesenchymal stem/stromal cell (MSC) injection has emerged as a minimally invasive biologic therapy with potential chondroprotective and regenerative effects; however, its capacity for structural cartilage repair remains uncertain. This narrative review summarizes clinical outcomes, with a focus on MRI-based cartilage morphological findings after MSC injection for knee OA. A MEDLINE search through January 30, 2025 identified 53 eligible clinical studies evaluating intra-articular MSC injections for knee cartilage lesions or OA, including 20 studies with MRI-based cartilage assessments. Most studies demonstrated significant improvements in pain and function, with benefits observed within 3-6 months and maintained up to 12-24 months. MSC therapy was safe and well tolerated. MRI findings were heterogeneous: most studies showed no significant structural improvement, while a limited number of studies reported cartilage preservation or modest increases in cartilage thickness. Advanced MRI techniques, including T2 mapping, occasionally detected improvements in cartilage quality. Intra-articular MSC injection provides consistent clinical benefits for knee OA, but current MRI evidence suggests limited and variable morphological cartilage restoration. Further standardized studies are needed to clarify its regenerative potential.