Chondrosarcoma arises either spontaneously in previously normal bone, or as a results of malignant change in a pre-existing non - malignant lesion, such as an osteochondroma or an enchondroma. that have predilection for this localisation,

The commonest site of Osteosarcoma are those of more active epiphyseal growth, the lower end of femur, upper end of tibia or fibula etc.