Anterior suprapatellar (quadriceps) fat pad impingement syndrome is a controversial cause of anterior knee pain although anterior suprapatellar fat pad edema may often, and possibly more commonly, be incidental 1,2.
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Clinical presentation
Patients present with anterior knee pain and with the point of tenderness at the superior pole of the patella. The pain is exacerbated on deep knee flexion.
Etiology
The etiology is unclear. It is suggested to result from repeated microtrauma resulting in fibrosis and hemorrhage. There is no significant correlation with patellofemoral maltracking 8. A recent study reported an association with patellofemoral joint degeneration 9.
Radiographics features
MRI
The anterior suprapatellar fat pad is edematous compared to the prefemoral fat pad, enlarged (≥10 mm AP diameter) with a mass effect on the adjacent suprapatellar recess (i.e. a convex border) and quadriceps tendon 1-4.
Signal characteristics
- T1: low signal
- T2: high signal
- T1C+: enhancement
The most common associated MRI findings are joint effusion and quadriceps tendinitis 11.
Treatment and prognosis
Initial management is usually conservative, like anti-inflammatory medications and decreased painful activities. Complete pain resolution can be achieved with ultrasound-guided injection of anesthetic or corticosteroid followed by physical therapy 6. Surgery could be considered in cases with persistent symptoms by laparoscopic resection 7.
Differential diagnosis
In the absence of anterior knee pain, quadriceps fat pad edema diagnosis cannot be made based solely on MRI findings 2,10.
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