Fig. 9.

Evolution of an early subchondral insufficiency fracture with osteonecrosis. a Initial radiograph shows a slight hyperostosis near a discrete depression of the lower pole of the condyle (arrow). b Additional radiograph tangent to the posteroinferior pole of the condyle and performed with traction on the leg shows a typical subchondral bone dissection (arrow). c Three months later, this necrotic area shows a focal collapse (arrows), already complicated by a complete narrowing of the adjacent joint space (arrowhead)