Representative sections showing different grades of integration of repair tissue to parent cartilage. Sections stained with Safranin O. Black arrows indicate the junction between repair tissue and parent cartilage. A) Poor repair tissue in the defect and no integration between this tissue and the parent cartilage. B) There is integration in this section but a hypocellularity at the junction with a small area of fissuring on the articular surface. C) Improved integration but hypocellularity at junction. D) Excellent integration between repair tissue (left hand side of arrow) and parent tissue (right hand side of arrow).