Patellar tendon-lateral femoral condyle friction syndrome
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Patellar tendon-lateral femoral condyle friction syndrome, also known as Hoffa fat pad impingement syndrome, is a common cause of anterior knee pain in active individuals. It is thought to be due to patellar maltracking or imbalance of the forces between medial and lateral vastus muscles, causing impingement of the superolateral aspect of Hoffa fat pad between the inferior patella and the lateral femoral condyle.
Patients present with anterior knee pain exacerbated by hyperextension and point tenderness at the inferior pole of the patella. The fat pad is thickened, which may make palpating the patella difficult 1.
It is usually occult on plain radiographs and CT.
Ultrasound usually shows echogenic edematous fat within the proximal lateral portion of Hoffa's fat pad.
Focal area of high T2 signal (edema) at the inferolateral aspect of the patellofemoral joint, within the superolateral portion of the infrapatellar fat pad. A cystic lesion can sometimes be found between the lateral femoral condyle and the lateral retinaculum. Associated findings include lateral patellar subluxation and patella alta, which are found in around 90% of cases 1,2.