Presentation
Left knee pain.
Patient Data
Narrowing of the medial joint compartment is noted. Irregularity of the superior pole of the patella is of uncertain significance. No further abnormality.
No signs of fractures. Diffuse low attenuation of the bones. There is a well-defined fat attenuated lesion within the upper pole of the patella, showing sclerotic margins, no cortical breach and no periosteal reaction, consistent with a nonaggressive lesion - this may be an intraosseous lipoma, which can be painful.
Further characterization with MRI may be considered.
Medial compartment joint space narrowing.There is a mild joint effusion.
In the patella, and there is a intraosseous lipoma.
There is a moderate joint effusion and chronic synovitis.
In the medial compartment of the knee, there is a chronic post root ligament tear of the meniscus associated with extrusion complicated by patchy grade 4 chondromalacia.
In addition, there is edema in the medial femoral condyle and an ill-defined subcortical line in the weight-bearing portion consistent with an insufficiency fracture.
In the lateral compartment, there is a horizontal tear through the posterior horn of meniscus associated with a parameniscal cyst that measures 5 mm in size.
Cruciate and collateral ligaments are normal there is a small Baker's cyst. No popliteal fossa mass.
Case Discussion
The radiograph barely demonstrated the nonaggressive lesion within the patella. Further CT scan could not spot fractures, as clinical suspected, but confirmed the benign appearances of the patellar lesion. The MRI spotted that the symptoms are probably due to a subchondral insufficiency fracture of the medial femoral condyle, in the setting of chronic medial meniscal dysfunction.
Intraosseous lipomas are rare benign lesions that account for less than 3% of all bone tumors.
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