61 patients with Kellgren-Lawrence grade II-III knee osteoarthritis were randomized to treatment with either a single intraarticular injection of bone morrow-derived mesenchymal stem cells (BM-MSC) or oral acetaminophen 500mg every 8 hours for 6 months. Patients were assessed for outcome on a visual analog scale for pain and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Patients were assessed 1 week, 1 month and 6 month follow-up. Results demonstrated significantly favourable results in the BM-MSC group compared to the acetaminophen group for VAS pain and the WOMAC Pain and Stiffness subscales at 1 weeks, 1 month, and 6 months, and for the WOMAC Physical function subscale at 1 month and 6 months.