Presentation
Pain in the anterior compartment of the left knee.
Patient Data
The MRI sequences demonstrate a well-circumscribed oblong shape mass within the infrapatellar (Hoffa's) fat pad measuring (24 x 22 x 7 mm). It appears isointense to the articular cartilage centrally with hypointense rim (calcification) peripherally on all sequences. Mild cortical irregularity with subchondral edema of the medial femoral condyle is noted.
Note mild edema of high signal within of the infrapatellar fat pad.
Normal appearance of both collateral and cruciate ligaments as well as the menisci.
Case Discussion
Intracapsular (osteo-)chondroma of the knee is a rare benign tumor of cartilaginous origin due to extrasynovial metaplasia, usually located within the infrapatellar fat pad.
The main differential diagnoses include:
localized tenosynovial giant cell tumor (also known as intraarticular giant cell tumor of the tendon sheath)
calcified synovial sarcomas
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