Di Martino, A., Di Matteo, B., Papio, T., Tentoni, F., Selleri, F., Cenacchi, A., Kon, E., Filardo, G. Platelet-Rich Plasma Versus Hyaluronic Acid Injections for the Treatment of Knee Osteoarthritis: Results at 5 Years of a Double-Blind, Randomized Controlled Trial. American Journal of Sports Medicine 2019; 2: 347-354