Two different radiological findings can be referred to as the “crescent sign.” One involves an indicator of a fracture along the point between cartilage and bone where it articulates with another bone, and the other refers to a characteristic sign of severe opportunistic infection in the lungs. The intended meaning is usually clear from context. X-ray, Magnetic Resonance Imaging (MRI), and other procedures may reveal the crescent sign at various stages.
In the case of the bone, this sign is most commonly observed along the femur, particularly at the hip joint. It takes the form of a curved crescent along the cartilage at the top of the bone, indicating that it is beginning to fracture and separate. This occurs as a result of avascular necrosis, where an interruption to the blood supply causes the tissue to start dying. Testing may identify the crescent sign early, providing more treatment options for the patient.
Treatments for avascular necrosis can depend on the level of advancement and the cause. They can include lifestyle adjustments for the patient, such as losing weight to reduce strain on the bone. Surgery may be necessary if inflammation occurs, to remove damaged tissue and rebuild part of the joint. Patients with blood vessel disorders might need evaluation to learn more about what is impeding circulation so it can be corrected to prevent further complications.
Infections in the pulmonary cavity can also cause a distinctive curved line that may show up in medical images. The most common reason for the crescent sign to develop is colonization with Aspergillus fungus. This infection is invasive and aggressive; it needs to be treated rapidly and with the most aggressive treatment options available. Antifungal medications may be an option, along with respiratory support to help the patient breathe if the fungal growth is large enough to impede pulmonary function.
Patients with an interest in their medical imaging studies can ask to see them and may request an explanation of the findings. A radiologist or technician can point out various physical structures and highlight the area of particular interest in the image or images. The crescent sign can be easy to spot, and the radiologist may have samples to show patients how the same area of the anatomy looks in healthy patients. Some people find these references helpful to understand the nature of the issue and learn more about how the doctor plans to treat it.