Step 1: In a bowl, mash up the fondant with the pink food colouring until it is light pink.
Step 2: Mould into the shape of a bent knee, and mould so that is it fairly realistic. A toothpick can be useful at this point.
Step 3: With the cheese grater, roughen up the area which is the mid centre of the knee.
Step 4: Dribble the red food colouring over the grated area.
Step 5: Serve your scraped knee!