Case contributed by Dr Jeremy Jones


Rugby injury 1 year ago. Flare-up over the last couple of weeks. Initially night pain, but that has settled.

Patient Data

Age: 15 years
Gender: Male

Rounded lucency in the lateral portion of the medial femoral condyle.  Otherwise, the knee is normal.


The rounded lucency on the x-ray is a predominantly low PD SI lesion with central high PD SI and peripheral low SI suggesting a sclerotic margin. Extensive surrounding bone marrow edema and adjacent soft-tissue edema. Appearances are most in keeping with a chondroblastoma. CT for confirmation of internal architecture suggested.


CT confirms a medial femoral condyle lucent bone lesion with sclerotic margin and central chondroid matrix. Chondroblastoma seems the most likely diagnosis.

Case Discussion

The appearances of the MRI and CT suggest chondroblastoma as the most likely diagnosis. A lucent bone lesion with surrounding edema and night pain might push people towards thinking about osteoid osteoma. However, the imaging appearances are definitely not of that.

Orthopedic biopsy was performed that confirmed the diagnosis.

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