Photomicrographs of the rats knee joint in the control group (a), placebo group (b, c, d, and e), and treated group (f); frontal section, staining by hematoxylin and eosin. In (a), articular cartilage showing regions: superficial (Cs), medium (Cm), deep (Cp), and calcified (CC). Compact bone (Oc) and bone marrow (Mo). In (b), the area of necrosis in the articular cartilage (dashed). In (c), hyperplasia of chondrocytes (Co) on articular cartilage. In (d), clones of chondrocytes (Cl) and flocculated surface cartilage (arrowhead). In (e), cracks in the cartilage matrix (star) and chondrocytes (black arrows). In (f), inflammatory infiltrate, with free and adhered leukocytes on the surface of the articular cartilage (white arrow). Articular cavity (Ca).