Osteochondral grafting is a procedure designed to treat defects in the articular cartilage lining if the knee joint. In this procedure a tunnel of bone is cored out of the base of the defect and a matching core of bone and cartilage is taken from a part of the knee where there is no actual joint between bones. The core of cartilage and bone is then impacted into the tunnel drilled in the base of the defect. The cartilaginous defect may be filled with articular cartilage attached to a bone block that heals to the sides of the tunnel providing support for the cartilage graft. This procedure is performed arthroscopically.