The exact causes of primary bone cancer are unknown. Research is continually being carried out to try to find the causes. As many bone cancers occur in teenagers and young people, it is thought that they may be related in some way to changes that occur when bones are growing.

People who have had previous high doses of radiotherapy to an area that includes bones, have a slightly increased risk of developing cancer of that bone. This is still a very small risk and most people who have radiotherapy will never develop a primary bone cancer.

People who have a type of long-term disease of the bone, known as Paget’s disease, have an increased risk of developing an osteosarcoma.

If a person has had a benign (non-cancerous) bone tumour known as a osteochondroma or a chondroma, they will have a slightly increased risk of developing a chondrosarcoma.

Most bone cancers are not caused by an inherited faulty gene, but some people with genetic conditions have an increased risk of developing bone cancer. People who have an inherited condition known as Li-Fraumeni syndrome have an increased risk of osteosarcoma and some other types of cancer. Children who have a rare type of eye cancer known as retinoblastoma, that is caused by an inherited faulty gene, have an increased risk of osteosarcoma. Another rare genetic condition called hereditary multiple exostoses (HME) can also increase the risk of developing chondrosarcoma.

It is sometimes thought that an injury or knock to a bone can cause cancer to develop, but there is very little evidence to suggest that an injury will cause bone cancer. An injury may draw attention to a bone cancer that is already there.