Which x-ray finding is characteristic of osteosarcoma?

Osteosarcoma is a type of malignant bone tumor that typically affects the long bones, particularly around the knee (distal femur and proximal tibia). A hallmark of osteosarcoma on an X-ray is the destruction of both the medullary (inner) and cortical (outer) bone. This radiographic finding reflects the aggressive nature of the tumor and its ability to invade the surrounding bone structure.

In osteosarcoma, one can also see a characteristic "sunburst" pattern of bone formation or periosteal reaction due to the rapid bone growth associated with the tumor. However, the destruction of normal bone architecture—both of the medullary cavity and cortex—is essential for the diagnosis. This destructive process often leads to a mixed lytic and blastic appearance on imaging, which is very distinct compared to other conditions.

While the other answer choices may relate to various bone or soft tissue conditions, they do not specifically represent the typical imaging findings associated with osteosarcoma. For instance, fractured bones can appear in several different scenarios, calcification in soft tissue can suggest other pathologies such as dystrophic calcification or calcifying tumors, and joint effusion is often seen with injury or inflammatory conditions but is not indicative