Periosteal Reaction

The periosteum is a thin membrane surrounding every bone except surfaces covered by cartilage. In response to injury or other stimuli, the periosteum forms new bone, in what is known as periosteal reaction. This is synonymous with other terms, such as periostitis, periosteal new bone formation, and reactive bone formation. Understanding the patterns of periosteal reaction can be useful for assessing the aggressiveness of the underlying lesion and formulating a differential diagnosis.