Safety and efficacy of umbilical cord-derived Wharton’s jelly compared to hyaluronic acid and saline for knee osteoarthritis: study protocol for a randomized, controlled, single-bl... oleh Ashim Gupta, Nicola Maffulli, Hugo C. Rodriguez, Eric W. Carson, Randa A. Bascharon, Kristin Delfino, Howard J. Levy, Saadiq F. El-Amin