Fig. (2) Picrosirius red staining. Normal menisci (horizontal sections of the central portion of menisci) had strong picrosirius red staining (top photos). In contrast, OA menisci (horizontal sections of the central portion of menisci) had moderate and weak picrosirius red staining mixed with blue counter staining (bottom photos). Note that the decrease of collagen staining occurred inside the OA menisci. Scale bar: 200 µm. (Inserts show age in years for male (M) and female (F) subjects in Figs. 2-8).