A small crater is located medially on the convex surface of the talus, next to the internal malleolus. A small (up to 1.1 cm long) osseous fragment is seen placed inside the crater, separated from the underlying bone. Both the lesions appear with sclerotic margins and a smooth contour (the latter slightly microlobulated regarding the osseous fragment).
Very small subchondral cysts accompany the perimeter of the crater. A second swallow indentation can be seen at the anterior upper aspect of the talus, also indicating chronic micro-injuries.
No other visible sign of fracture was revealed in the study above.
The findings are consistent with osteochondritis dissecans of the talus, stage III (complete separation, no displacement).
Annotated 3D Image: The red lines show the contour of the crater. The black line indicates the osseous fragment.
All images are courtesy of Dr Ioannis Vasilakis, MD PhD, Radiology (GRE)