Chondroblastoma is diagnosed by X-ray examination. Have characteristic, tumor confined to the origin of the epiphysis, the epiphyseal cartilage rarely penetrating metaphyseal arrival. At the general end of the central or eccentric bone parts were oval or circular lesions damage. Often one sector of the hardening clear edge overcast. Possible expansion of a small number of eccentric cortical lesions, and there is dense periosteal reaction, the whole film paste for osteoporosis tumor spread irregularly shaped area of calcification, as many floccus cavity shape, but no giant cell tumor with a clear separation of changes in trabecular bone. And giant cell tumor of a different, new bone formation at the bottom of Cancer is the backbone of the cortex, the longest course more obvious periosteal reaction. Most arise in site include the proximal femur, proximal tibia, distal femur and proximal humerus.