Figure 4: Photomicrographs of the rats’ knee joints in the control group (a), placebo (b and c), and treated (d), the frontal section stained by hematoxylin and eosin. In (a), the synovial membrane (Ms) and the underlying loose connective tissue with blood vessels (white arrow) and collagen fibers (black arrow); blanks are characteristic of tissue type, but some of them represent cytoplasm of adipocytes, which do not stain due to technique. In (b), pannus in the synovium, the synovial membrane covering the underlying connective tissue and the hollow arrow shows that the synovial cell disengaged from the epithelium. In (c), panus adhered on the surface of the articular cartilage (Pn), chondrocytes (arrowhead) in the cartilage matrix. In (d), slight recovery of the synovium with decreased synovial infiltration and reorganization of collagen fibers (Co) in connective tissue. Articular cavity (Ca).