Background: Degenerative Knee Osteoarthritis (KOA) is a major cause of pain and disability, and effective joint-preserving therapies for moderate (Kellgren-Lawrence [KL] grade 2-3) disease remain limited. Bone Marrow Aspirate Concentrate (BMAC) has emerged as a regenerative treatment option, and intra-articular BMAC injection for KOA was recently approved in Korea through the New Health Technology Assessment (NHTA). However, real clinical evidence in the Korean population remains limited. This study provides early real-world clinical evidence of BMAC therapy in a routine clinical settingMethods: This study is an interim analysis of an ongoing retrospective observational case series (target n = 62) conducted at a single orthopedic center. Eleven consecutive patients with Kellgren-Lawrence (KL) grade 2-3 KOA who failed conservative treatment were included between January 2024 and 2025. All patients (2 males, 9 females; mean age 58.55 ± 5.85 years) received a single intra-articular injection of autologous BMAC prepared using the NovaStem system. The primary endpoint was the change in Visual Analog Scale (VAS) score at 1 day post-procedure (discharge). Secondary observations included follow-up outcomes at 1, 3, 6, and 12 months. Pain severity was assessed using VAS at baseline and at 1 day post-procedure (discharge). Pre- and post-treatment VAS scores were compared using a paired t-test following assessment of normality, with significance set at p < 0.05. Patients were followed up for up to 12 months to determine whether there was any improvement in pain or adverse reactions.Results: The mean baseline VAS score significantly decreased from 5.00 ± 0.63 to 2.82 ± 0.60 at the post-treatment (mean difference, 2.18; 95% CI, 1.63-2.73; p < 0.0001). A clinically meaningful improvement (?2-point VAS reduction) was observed in 81.8% (9/11) of patients. This reduction exceeded the established minimal clinically important difference for KOA. No serious adverse events were reported. Limited follow-up data suggested variable durability, with some patients requiring additional surgical intervention. Conclusion: Intra-articular BMAC injection using the NovaStem system demonstrated significant short-term pain reduction in patients with moderate KOA in our clinical setting. Intra-articular BMAC injection appears to be a safe and suggests a potential role as a joint-preserving option for patients with KL grade 2–3 knee OA who have not responded to conservative care. These findings represent early clinical evidence following NHTA approval, providing in vivo evidence supporting BMAC as a novel regenerative therapy in orthopedic practice. Larger cohort analysis and longer-term follow-up are needed to confirm durability and functional outcomes.