There are three fat pads around the knee that can become impinged and can be symptomatic.
Which Three Fat Pads?:
- Suprapatellar
- Quadriceps and
- Hoffa’s fat pads.
What is the MRI Appearance :
- Normal fat pads are High Signal on PD and will be dark on PDFS as they will completely fat saturate.
- When they are impinged, look for high PDFS signal in these regions.
What does a normal fat pad look like?
Image Above: Location for quadriceps fat pad ( Blue Arrow), Suprapatellar Fat Pad ( Pink arrow) and Hoffa’s Fat Pad ( yellow arrow). Normally will be dark on T2FS/PDFS as fat will saturate out.
What does an impinged fat pad look like?
Image Above: Impingement of quadriceps fat pad ( yellow arrow). Due to swelling the posterior margin can become convex ( blue arrow).
Image Above: Impingement of suprapatellar fat pad ( yellow arrow). Same appearance as impingement elsewhere.
Image Above: Impingement of Hoffa’s fat pad ( yellow arrow).