If a cartilage defect is too large to be treated by an autograft, an osteochondral allograft may be required. Performed through an open incision, this procedure is similar to mosaicplasty, but the graft is taken from a cadaver donor. The graft is carefully sterilized and prepared before implantation and must match the anatomy of the patient. It is then shaped to fit the exact contour of a patient’s defect.