In radiology, the crescent sign is a finding on conventional radiographs that is associated with avascular necrosis. [1] [2] [3] It usually occurs later in the disease, in stage III of the four-stage Ficat classification system. [1] It appears as a curved subchondral radiolucent line that is often found on the proximal femoral or humeral head. [1] Usually, this sign indicates a high likelihood of collapse of the affected bone. [1] The crescent sign may be best seen in an abducted (frog-legged) position. [1] [4]
The crescent sign is caused by the necrotic and repair processes that occur during avascular necrosis. [1] [2] Osteosclerosis occurs at a margin where new bone is placed over dead trabeculae. [1] When the trabeculae experience stress leading to microfractures and collapse, the crescent sign appears. [1]
The crescent sign may be seen with other bone diseases, such as shear fractures. [1]
In radiology, the crescent sign is a finding on conventional radiographs that is associated with avascular necrosis. [1] [2] [3] It usually occurs later in the disease, in stage III of the four-stage Ficat classification system. [1] It appears as a curved subchondral radiolucent line that is often found on the proximal femoral or humeral head. [1] Usually, this sign indicates a high likelihood of collapse of the affected bone. [1] The crescent sign may be best seen in an abducted (frog-legged) position. [1] [4]
The crescent sign is caused by the necrotic and repair processes that occur during avascular necrosis. [1] [2] Osteosclerosis occurs at a margin where new bone is placed over dead trabeculae. [1] When the trabeculae experience stress leading to microfractures and collapse, the crescent sign appears. [1]
The crescent sign may be seen with other bone diseases, such as shear fractures. [1]