You are shown a sagittal T1 (image 1) and a sagittal proton density fat suppression water-weighted image (image 2) of the knee of a 61-year-old.
- What are the arrows indicating?
- What other abnormality is odd about the patella?
Sagittal T1
Sagittal T2
- The arrows point to an area of linear penetrating upper pole class 4 chondromalacia.
- What is odd about the patella is that the medullary space is subtly but definitely swollen on the water-weighted image. The swelling is diffuse and far greater than that expected for a simple, thin penetrating erosion.
- Follow-up question: Other explanations that may account for such swelling might include:
- a. Unrecognized trauma or minor fall with contusion
- b. Reactive swelling from concomitant CPPD within the erosion
- c. Gout
- Answer: C. Gout
- ProScan Pearl: Don’t try to make a finding into something it is not. In other words, with no history of trauma, trauma is an impossible choice. The edema as a simple chondromalacic reaction could not be explained by this one erosion. For more case review, check out MRI Online.
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