Presentation
Left knee swelling for 3 months with suspected ganglion cyst
Patient Data
Contrast-enhanced MRI of knee joint shows a well defined T2 and PD fat-sat hyperintense lesion involving lateral half of infrapatellar fat pad (Hoffa's fat pad) with focal extra-articular extension.
The lesion is isointense on T1 weighted image. There are thin T2 hypointense septations within the lesion. Focal nodular T2 hypointensity is noted within the inferolateral portion of the lesion, which corresponds to calcification or phlebolith. The lesion showed moderate heterogeneous contrast enhancement.
No further intra-articular extension of the lesion noted.
Magnified lateral radiograph of left knee joint shows an ill-defined faint opacity of the infrapatellar region posterior to the patellar tendon.
A small focus of calcification projected over the infrapatellar fat pad, corresponding to a phlebolith.
Case Discussion
A young adult female patient presented with mild swelling of the left knee joint in infrapatellar region. She was sent for MRI of the knee with the suspicion of a ganglion cyst.
MRI images show a well defined PD fat-sat hyperintense, T2 hyperintense and T1 isointense lesion in the lateral portion of the infrapatellar fat pad with focal extra-articular extension, showing moderate heterogeneous enhancement and tiny phlebolith (correlated with radiograph).
These imaging features are consistent with a hemangioma of the infrapatellar fat pad.
Many tumors and tumor-like conditions can affect the infrapatellar fat pad e.g. ganglion cyst, hemangioma, chondroma, osseous metaplasia and synovial sarcoma.
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