Fat pad impingement syndromes of the knee

Last revised by Daniel J Bell on 30 Nov 2021

In fat pad impingement syndromes, the etiologies are different for each knee fat pad.

In anterior suprapatellar fat pad impingement syndrome, the cause is usually due to either a developmental cause related to the anatomy of the extensor mechanism or may be related to abnormal mechanics. In this syndrome, the posterior border of the anterior suprapatellar (quadriceps) fat pad is high signal on PD MRI and convex with a mass effect upon the suprapatellar bursa.

In infrapatellar fat pad impingement syndrome (Hoffa disease) the cause is usually due to single or repetitive traumatic episodes; the inflamed fat pad then becomes hypertrophied with a predisposition to impingement between the tibia and femur, and thus to further injury (a vicious circle).

In prefemoral fat pad impingement syndrome, the cause is either secondary to a prominent suprapatellar osteophyte, with the edema usually in the superior aspect of the prefemoral fat pad close to the midline or secondary to patellar tendon-lateral femoral condyle friction syndrome, with the edema, usually in the inferolateral aspect of the fat pad.

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