MR imaging of extrasynovial inflammation and impingement about the knee.

The knee has unique anatomy regarding the relationship between the synovial and capsular layers, with interposed fat pads at certain locations. The extrasynovial impingement and inflammation syndromes about the knee are underdiagnosed and should be included in the differential diagnosis of anterior knee pain. MR imaging is the best imaging modality for evaluation of the anatomy and disorders of these extrasynovial compartments.