Lee NH, Na SM, Ahn HW, et al. - This research was sought to correlate the outcome of cartilage regeneration between bone marrow aspirate concentrate (BMAC) augmentation and allogeneic human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) transplantation in high tibial osteotomy (HTO) with microfracture (MFX) for medial unicompartmental osteoarthritis (OA) of the knee in the young and active patient. Researchers enrolled the patients who had undergone HTO and arthroscopy with MFX combined with BMAC or allogeneic human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) procedure for medial unicompartmental OA with a kissing lesion which was shown full-thickness cartilage defect (≥ International Cartilage Repair Society (ICRS) grade 3B) in medial femoral cartilage and medial tibial cartilage between January 2015 and December 2019. Clinical outcomes were compared, including Hospital for Special Surgery (HSS) score, Knee Society Score pain and function, and Western Ontario and McMaster Universities Osteoarthritis Index score between BMAC and hUCB-MSCs group at a minimum of 1 year follow up. The results of this study indicate that the hUCB-MSC procedure was more effective than the BMAC procedure for cartilage regeneration in medial unicompartmental knee OA even though the clinical outcomes improved regardless of which treatment was administered.