Loose fragments and other debris: miscellaneous synovial and marrow disorders.

Conventional MR imaging evaluation of the knee focuses mainly on the effects of acute trauma and degenerative conditions. Numerous other conditions that affect the knee may mimic clinical characteristics of common traumatic and degenerative disorders. Synovial and marrow abnormalities are frequently encountered and often unsuspected on routine MR imaging studies of the knee. This article presents the MR imaging appearance of the normal synovium, bone marrow, and commonly encountered abnormalities of these structures.