Currently, most knee meniscal tears are treated by partial or complete meniscectomy, or by suture repair when it is possible. Recently, the investigators have successfully developed and implanted a novel biomaterial, platelet-rich fibrin (PRF), to treat articular cartilage defect in pigs. The PRF is autogenesis as a natural fibrin-based biomaterial favorable to the development of microvascularization and enables local and progressive delivery of growth factors providing unique properties for tissue remodeling and wound healing. The advantages of using PRF implantation include no transplant rejection and no need to perform second operation. Knee meniscal repair using PRF has not been reported before. The aim of this study is to investigate whether PRF implantation can facilitate regeneration process of meniscectomized knee and T2-map MRI can monitor the process in those patients with meniscal tears.