MR appearance of distal femoral cortical irregularity (cortical desmoid)

Purpose: Our goal was to describe the MR appearance of distal femoral cortical irregularity (DFCI). Method: With plain radiographs and MR images of 100 knees, the presence of DFCIs was determined, and the shapes of DFCIs were classified into three subgroups: concave, convex, and divergent cortical shapes. Radiographic and MR shapes of DFCIs were compared. Results: DFCIs were shown in various shapes on both the radiographs and the MR images. Forty-four DFCIs were found both on radiograph and by MR image. An additional 14 DFCIs were identifiable only on MR images. However, the majority of DFCIs showed an association between radiographic and MR shapes. MRI revealed that all 58 DFCIs were located at the attachment site of the medial gastrocnemius muscle. DFCIs were enhanced in three of the four patients who underwent postcontrast MR study. Conclusion: A good understanding of radiographic and MR findings of the DFCI may be of great help in the differential diagnosis of distal femoral lesions.