What does it mean to elevate the periosteum?

Answer 1

The periosteum is a layer of connective tissue and bone cell precursors that overlies the bone itself. Excess growth between the periostem and bone can cause the periosteum to separate from the underlying bone. This elevation of periosteum forms a triangular shape when viewed in a radiograph (xray), and is often called Codman's triangle.

Periosteal elevation is commonly associated with a cancer called osteosarcoma, but may also be seen in other diseases.