Osteosarcoma often starts at the ends of the long bones, where new bone tissue forms as a young person grows. Any bone in the body can be affected, but the most common sites are in the arms and legs, particularly around the knee and shoulder joints.
There are several different types of osteosarcoma. Most occur in the centre of the bone. There are also rare subtypes, such as parosteal, periosteal, telangiectatic, and small cell osteosarcoma.