Abstract：Platelet-rich plasma (PRP) has a lot of active growth factors, which can stimulate the proliferation of chondrocytes, promote the proliferation and migration of cartilage precursor cells, induce cartilage precursor cells differentiate into chondrocytes, promote collagen synthesis as well as inhibit the inflammatory response and degeneration of cartilage, provide an internal environment conductive to cartilage repair and delay disease development. In recent years, PRP injection has become a new choice for the treatment of osteoarthritis (OA), and has significant therapeutic effect. To further increase its effectiveness, PRP injection therapy has been performed not only in the articular cavity but also under the subchondral bone. Subchondral bone lesions will accelerate cartilage loss, so it is necessary to consider subchondral bone as one of the key points of the pathogenesis and pathological process of OA. In this paper, the bioeffects of PRP and the application of PRP injection in the treatment of knee osteoarthritis (KOA) were reviewed. Meanwhile, this paper prospected the research of PRP treatment which was injected under the subchondral bone for KOA, to seek more effective methods for the treatments of KOA.