title: Authors' reply.
authors.affiliation: Seoul, South Korea.
authors.forename: Yong-Gon
authors.initials: YG
authors.lastname: Koh
authors.affiliation: Seoul, South Korea.
authors.forename: Yun-Jin
authors.initials: YJ
authors.lastname: Choi
mesh_terms: D005260:Female; D006801:Humans; D008297:Male; D045164:Mesenchymal Stem Cell Transplantation; D020370:Osteoarthritis, Knee / Q000601:surgery*; D053657:Platelet-Rich Plasma