Crescent sign

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title: "Crescent sign" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["musculoskeletal-radiographic-signs"] description: "Pattern seen in radiologic examinations" topic_path: "general/musculoskeletal-radiographic-signs" source: "https://en.wikipedia.org/wiki/Crescent_sign" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Pattern seen in radiologic examinations ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/4/4c/Crescent_sign_annotated.jpg" caption="A radiograph of a left hip joint, which reveals a thin, curvilinear lucent line parallel to the cortical margin of the femoral head, in a patient with avascular necrosis."] ::

In radiology, the crescent sign is a finding on conventional radiographs that is associated with avascular necrosis. It usually occurs later in the disease, in stage III of the four-stage Ficat classification system. It appears as a curved subchondral radiolucent line that is often found on the proximal femoral or humeral head. Usually, this sign indicates a high likelihood of collapse of the affected bone. The crescent sign may be best seen in an abducted (frog-legged) position.

The crescent sign is caused by the necrotic and repair processes that occur during avascular necrosis. Osteosclerosis occurs at a margin where new bone is placed over dead trabeculae. When the trabeculae experience stress leading to microfractures and collapse, the crescent sign appears.

The crescent sign may be seen with other bone diseases, such as shear fractures.

References

References

1. (2000). "The musculoskeletal crescent sign". Radiology.
2. (1985). "Pathogenesis of idiopathic osteonecrosis: The ubiquitous crescent sign". The Orthopedic Clinics of North America.
3. (1963). "The Radiolucent Crescent Line--An Early Diagnostic Sign of Avascular Necrosis of the Femoral Head". Bulletin of the Hospital for Joint Diseases.
4. "Rheumatology Image Bank: Avascular Necrosis, Crescent Sign: Ficat Stage III, Hip".

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::