R adiography is the baseline modality in the evaluation of bone diseases, commonly followed by radioisotope scanning, CT, or MRI. Accelerated development of MRI and the initially low-resolution imaging capability of sonography may have resulted in the underutilization of sonography for bone diseases. 1 However, MRI itself does not have the fine resolution of plain radiography or CT to define cortical abnormalities of bone. The use of sonography for evaluation of the skeletal system has been hampered by the misconception that the lack of propagation of ultrasound through the bone and small field-of-view images are insurmountable obstacles to evaluate the skeletal system, resulting in reduced use and a lack of literature on musculoskeletal sonography (MSUS). Nevertheless, the high reflectivity of sound at the bone-soft tissue interface and tomographic nature of sonography make it ideal for evaluation of bone contours. 2 High-resolution sonography can reveal subtle changes of the bone surface not detected on plain radiographs, such as tiny periosteal reactions and subperiosteal fluid collections, and can differentiate soft tissue lesions from bone lesions (Figure 1).
Using the extended-field-of-view function of MSUS, a large lesion can now be displayed on a