Cysts, geodes, and erosions.

Subchondral cystic lesions are common features that are associated with many arthropathies and synovial-based processes. Although not comprehensive in scope, this article correlated the pathophysiology and imaging features of several of these disorders to better understand the associated subchondral lucencies. The imaging features of these subchondral cystic lesions were described in each process, and, in some cases, demonstrated overlapping features. By becoming familiar with the disease processes and recognizing the imaging appearances and associated clinical findings, the radiologist will be better able to differentiate these benign entities from more aggressive processes, such as tumor. Subchondral cystic lesions are common features that are associated with many arthropathies and synovial-based processes. Although not comprehensive in scope, this article correlated the pathophysiology and imaging features of several of these disorders to better understand the associated subchondral lucencies. The imaging features of these subchondral cystic lesions were described in each process, and, in some cases, demonstrated overlapping features. By becoming familiar with the disease processes and recognizing the imaging appearances and associated clinical findings, the radiologist will be better able to differentiate these benign entities from more aggressive processes, such as tumor.