A rare case of Hoffa's fat pad herniation in a young patient: dynamic ultrasound and MRI diagnosis

: Hoffa's fat pad (HFP) is part of the knee structure interposed between the joint capsule and the synovium. Recent studies have classified infrapatellar fat pad (IFP) disorders on a pathogenesis-based classification: traumatic disorders, post-traumatic disorders, lesions secondary to adjacent disorders. Masses or pseudo-masses may also be found within the IFP, however these alterations are much less frequent. Diagnostic imaging plays an important role in the diagnosis of masses and pseudo-masses of IFP and the first choice exam is a dynamic ultrasound study. We presented a rare case of Hoffa's fat pad herniation through the joint capsule, in a young child without history of knee injuries that has never been described before in the literature.