Presentation
Palpable lump at the right distal thigh.
Patient Data
There is a pedunculated bony mass arising from the medial aspect of the distal femoral metaphysis and projecting away from the epiphysis. It shows a lobulated margin with ring and arcs calcification. No pathological fracture is seen. A small adjacent fibrous cortical defect is noted.
The MRI sequences demonstrate that the medullary cavity, as well as the cortex of the bony lesion, are in continuity with those of the parent bone with thinning of the cortex. No fracture or adjacent soft tissue mass or abnormal enhancement on postcontrast sequences.
The cartilage cap is well-identified on T2WI/STIR sequences and measures less than 8 mm in thickness in this case. The distal component of the bony lesion protrudes into the adjacent vastus medialis muscle.
Note the adjacent fibrous cortical defect is also well visualised on the MRI sequences.
Case Discussion
Radiographic and MRI features are characteristic of an osteochondroma of the distal femur, which is considered as the commonest location (30%).
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