Primary osteosarcoma typically occurs in young patients (10-20 years) with 75% occurring before the age of 20.  

This is logical because the growth centers of the bone are more active during the puberty to adolescence time period.

The usual location is in the metaphyseal regions of long bones, and have a strong predilection for the knee, with up to 60% at this site.

The tumor typically causes:

• medullary and cortical bone destruction
• a wide zone of transition, permeative or moth-eaten appearance
• aggressive periosteal reaction including both sunburst type and Codman triangle (as in this case)