Background: Osteoarthritis (OA) is the most common degenerative joint disease for which there is no permanent treatment. The most affected structures are articular cartilage and subchondral bone. Knees are the most affected by OA, thus leading to severe disability. N-Acetyl phenylalanine glucosamine (NAPA) is a derivative of glucosamine (GlcN), which is one of the components of glycosaminoglycans ...