[Correspondence] Revisiting platelet-rich plasma for knee osteoarthritis – Authors' reply

We thank Guilherme Corrêa de Araújo Moury Fernandes and colleagues for their response to our Seminar,1 and their discussion of the use of platelet-rich plasma for the management of knee osteoarthritis. We agree that not all platelet-rich plasma is equivalent. Platelet-rich plasma is an autologous blood product prepared from patients’ whole blood, comprising platelets, leukocytes, growth factors, and cytokines. Its composition depends on the concentration of the constituents in whole blood, and on the manufacturing procedure, which differs in centrifugation protocol, addition of activators, and other factors.