Explanation

An osteosarcoma is a tumour that grows in your bone. Osteoblasts and osteoclasts work in harmony to shape your bones as you grow, and keep them healthy and strong. But, if you have osteosarcoma, the osteoblasts grow out of control and keep making new bone, even if you don't need it. The bone starts pushing on muscles and other parts of your body around it.

They most often grow in your thigh bone - your femur. The next most common places are in your upper arm, - your humerus - and shin bone - your tibia.