What are the two most likely aetiologies?
Low grade chondral lesion (e.g. enchondroma) or bone infarct.
The pertrochanteric left femoral fracture has been fixed with a long intramedullary nail and no periprosthetic complication noted (not shown). There is a single distal cross bolt in good position. Again noted is made of the 18 mm coarse clump of calcification, seen on the lateral radiograph and thought to be within the lateral femoral condyle.