Osteonecrosis is a common disorder of bone, which if left untreated, will lead to progressive collapse of bone, and degeneration of the overlying articular cartilage. Recently, new techniques have been developed in which the osteonecrotic lesion is drilled (core decompression) and/or more extensively debrided, and osteoprogenitor cells from the iliac crest are harvested, concentrated and delivered to the lesion to enhance bone healing. In the earlier stages of osteonecrosis of the hip and knee without collapse or arthritic changes in the involved joint, the intermediate term results for preserving (rather than replacing) the joint using these techniques have been very encouraging. Future basic and clinical research is necessary to develop evidence-based algorithms to optimize patient selection, cell harvesting, expansion and delivery, preparation of the osteonecrotic lesion, biomechanical support and appropriate rehabilitation protocols.