Fig. 6

Co-occurrence analysis of nonsurgical treatment of knee OA. a Mapping on keywords in the study on nonsurgical treatment of knee OA; the size of the icons indicates the frequency, and the keywords are classified into five clusters: articular cartilage study (red color), biomechanics study (blue color), physiotherapy study (green color), oral pharmacologic study (yellow color) and intra-articular injection study (purple color). b Distribution of keywords according to their time of appearance; keywords in purple appeared earlier than those in green, and keywords in yellow appeared later