Hoffa’s syndrome (Hoffa’s fat pad disease) is an impingement syndrome with Hoffa’s infrapatellar fat pad being crushed between the femoropatellar and femorotibial articular surfaces.


Synonym: liposynovitis prepatellaris


Risk factors:

(1) runners

(2) other causes of acute and/or repetitive trauma to the fat pad

(3) any cause of joint space narrowing


Clinical findings:

(1) anterior knee pain with or without discomfort behind the patella

(2) joint weakness

(3) extension of the bent knee is often painful

(4) variable knee swelling


Initially there is an acute phase which may be followed by chronic inflammation with scarring.


Findings on MRI:

(1) areas of increased signal intensity of T2-weighted MRI (due to edema and hemorrhage) in the infrapatellar fat pad

(2) bowing of the patellar tendon

(3) small joint effusion

(4) fibrotic trabeculae


Differential diagnosis includes:

(1) intra-articular synovial lipoma

(2) villous lipomatous proliferation of the synovial membrane (lipoma arborescens)

(3) knee ligament injury


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