Clinical and imaging outcomes after arthroscopic marrow stimulation followed by autologous bone marrow-derived mesenchymal stromal cell and hyaluronic acid injection in knee osteoarthritis: a prospective case series

Introduction Microfracture is commonly used to treat knee chondral defects but often produces fibrocartilage with unsatisfactory long-term outcomes. Bone marrow mesenchymal stromal cells (BMSCs) may enhance cartilage regeneration when combined with marrow stimulation, but their benefit in knee osteoarthritis (OA) remains unclear. Objectives To evaluate clinical and magnetic resonance imaging (MRI) outcomes of intra-articular BMSC and hyaluronic acid (HA) injection after arthroscopic marrow stimulation for mild-to-moderate knee OA. Methods This prospective, single-arm, single-center case series included patients with knee OA treated with arthroscopic microfracture. Two weeks postoperatively, cultured autologous BMSCs with HA were injected intra-articularly. MRI at 3 and 12 months assessed tissue regrowth and Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) scores; Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), 36-Item Short-Form Health Survey (SF-36), and Knee Society Score (KSS) were assessed through 12 months. Results Twenty patients (4 men, 16 women; mean age, 56.4 years) were enrolled. Tissue regrowth increased from 41% ± 28% at 3 months to 67% ± 28% at 12 months ( P < .001), and MOCART scores improved from 34.6 ± 16.4 to 45.2 ± 17.6 ( P = .002). WOMAC scores improved from 87.6 at baseline to 64.1 and 51.9 at 9 and 12 months. KSS and SF-36 scores were unchanged, with no serious adverse events. Conclusions Arthroscopic marrow stimulation followed by BMSC and HA injection was associated with improved MRI-based cartilage-repair parameters and WOMAC scores at 1 year. Without a control group and with concurrent interventions, BMSCs' specific contribution cannot be determined; findings are exploratory.