Osteochondral allograft transplantation in the knee.

Fresh osteochondral allograft (OCA) transplantation has over a 100-year clinical history. Many clinical and basic scientific studies have been performed with the result that allografting is now a part of the "cartilage repair paradigm" for the treatment of chondral or osteochondral lesions. In the knee joint, allografting has also been successfully used in complex joint reconstruction for the treatment of osteonecrosis, fracture malunion, and selected cases of osteoarthritis. Unlike many other cartilage repair techniques, OCA have the ability to restore mature, hyaline articular cartilage to the affected area. By virtue of their composite structure (cartilage and bone), allografts also can restore diseased or damaged bone often present in large or complex lesions. Nevertheless, OCA present unique and important difficulties in their clinical application, such as allograft tissue availability, safety issues, and immunologic response to the graft. Ongoing investigations continue to clarify the indications, surgical techniques, and clinical outcomes of fresh OCA.