RecruitingBiological interventionBone Marrow Aspirate Concentrate (BMAC)Treatment for Knee OsteoarthritisThe purpose of this study is to investigate the safety and effectiveness of bone marrow aspirate concentrate (BMAC) in patients with moderate to severe osteoarthritis of the knee. BMAC provides a rich source of mesenchymal stem cells (MSCs) and is a stem cell-based therapy that has been reported to preserve or improve the structure of joints. The Angel System is the device used in this study to concentrate bone marrow from the patient and is intended to separate a mixture of blood and bone marrow and collect plasma rich platelets preoperative to a surgical procedure. The goal of this study is to identify whether BMAC can be an effective and safe treatment for patients with osteoarthritis of the knee.