MR-IMAGING OF THE INFRAPATELLAR FAT PAD OF HOFFA

The infrapatellar fat pad of Hoffa is an intracapsular structure that is routinely visualized on magnetic resonance images of the knee. Beca use disease in this region is not uncommon, it is important to be fami liar with the various pathologic entities that may occur here, Abnorma lities that: are intrinsic to this fat pad include Hoffa disease, intr acapsular chondroma, localized nodular synovitis, postarthroscopy and postsurgery fibrosis, and shear injury. In addition, the infrapatellar fat pad may be involved secondarily from extrinsic processes, includi ng articular disorders leg, joint effusion, intraarticular bodies, men iscal cyst, ganglion cyst, cyclops lesion), synovial abnormalities leg , pigmented villonodular synovitis; hemophilia synovial hemangioma; pr imary synovial chondromatosis; chondrosarcoma; Lipoma arborescens; rhe umatoid, seronegative, and septic arthritis; arthritis associated with inflammatory intestinal disorders; synovitis associated with primary osteoarthritis), and anterior extracapsular abnormalities. The approac h to pathologic processes involving the infrapatellar fat pad of Hoffa is simplified when one is familiar with regional anatomy and possible differential diagnostic considerations.