The 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.

This is a pilot open-label, non-randomized, single institution study of BMAC administration in patient's with moderate to severe osteoarthritis of the knee who will undergo total knee replacement. Several weeks prior to total knee replacement, patients will have a sample of bone marrow taken from their pelvic region and concentrated using an investigational device called the Arthrex Angel Concentrated Platelet Rich Plasma (cPRP) System also known as the Angel System. The concentrated bone marrow will be immediately delivered back to the patient arthroscopically to the knee of interest. Blood and tissues samples will be collected at scheduled visits for molecular and histological analysis. Adverse events will be monitored throughout the trial. Assessment of healing will be performed by physical exam and standardized questionnaires related to the health of the patient.

Inclusion Criteria:

1. Kellgren Lawrence radiographic grade IV
2. Need for a total knee arthroscopy by the patients primary care provider/or orthopedist.
3. Persistent pain in target knee that is unresponsive to standard of care including acetametaphine, non-steroidal anti-inflammatory drugs, physical therapy and/or intraarticular corticosteroids and/or hyaluronic acid preparations.
4. Males or females aged 45-75.

Exclusion Criteria:

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