Appendix 4: Classic Signs and Findings in Musculoskeletal Radiology

Many musculoskeletal conditions are associated with specific imaging findings that allow a radiologist to diagnose these conditions with greater accuracy when he or she recognizes the patterns. These signs are often likened to non-radiologic objects, which may resemble them in shape or other features, or may be associated with the person who first established the association. Over time, these signs have become so common in helping diagnose certain conditions that they are part of the classical description, and they can help shorten the description of lengthy imaging findings into succinct, commonly understood phrases. To best apply a classic sign to an imaging study, it is important to understand the proper imaging modalities on which it can be detected, the characteristics necessary to qualify for the sign and the condition associated with the sign. This appendix describes the appropriate name of each sign; the condition with which it is associated; either the first reference in the literature that describes the sign or a newer reference that formally recognizes and names the sign; and a brief description of the sign.