Sunburst periosteal reaction is aggressive periostitis, occurs when the lesion grows too fast and the periosteum does not have enough time to lay down a new layer and instead the Sharpey’s fibers stretch out perpendicular to the bone.
It is frequently associated with osteosarcoma and other aggressive lesions such as an Ewing sarcoma or osteoblastic metastases.
Below xray shows
An ill-defined sclerotic lesion affecting the metaphysis of distal fibula and tibia with an aggressive periosteal reaction (sunburst type) and wide zone of transition.
It is associated with a large soft tissue swelling.
Sunburst appearance… Osteosarcoma