Generally speaking, fibrous bone cortical defect has no obvious clinical manifestations, and a few patients may have local pain and swelling, which will be aggravated after exertion. 1. In the early stage, the surface of bone cortex is blurred with irregular defects, some of which are round and some of which are oval. 2. In the second stage, the defect will gradually increase in size, and a ring-like sclerotic border will gradually appear around the defect. 3. In the third stage, the defects will progress to the other end of the spectrum and will gradually decrease in extent. However, some lesions do not shrink and may even grow toward the marrow cavity. Fibrous bone cortical defects are benign lesions that can generally heal on their own, and if the patient has no obvious clinical manifestations, regular review does not require special treatment. Surgery is required if the patient develops significant discomfort.