A piece of bone transplanted to another part of the skeleton where it is needed to improve function or strengthen the structure of the area. Sometimes a bone graft is taken from a cadaver, but usually it is harvested from the patient for which it will be used. Aside from blood, bone is the most frequently transplanted tissue in humans. Bone grafts are typically harvested from the patient's iliac crest (top of the hip bone), ribs, or fibula in the lower leg.