Fig. 10.

a, b, c, d, e, f, g, h AVN. A 53-year-old woman with pain during mobilization of the right knee; MRI has raised the suspicion of AVN (bone infarct) and we can note the evolution of the findings over 4 years. T1w (a) and proton density fat–suppressed (PD-FS, b) imaging show two areas of altered signal in the distal end of the femur and in the proximal end of the tibia with irregular morphology and inhomogeneous structure (*), with a peripheral rim, hypointense in T1w (arrows) and hyperintense in PD-FS (arrows) imaging corresponding to the reactive interface along the margin of infarct. Three months after the previous MRI (c, T1w and d, PD-FS), a further increase in the interface (arrows), a reduction in the ischemic area and signs of regeneration of the cancellous bone are observed. While the MRI findings are well evident, the CT performed in the same period (e) shows only a limited rarefaction (*) of the cancellous bone. One year later (f, T2w-FS) the infarct outcome area is still evident but smaller compared to previous examinations. Four years later (g, PD and h, STIR) the infarct zone appears less extensive and more shaded, but still present; the interface appears larger. ELMSI had not been detected for all 4 years and the patient progressively underwent an improvement in the clinical situation, with the disappearance of the pain. It is important to underline that ELMSI represents a fundamental indicator of a subchondral fracture and a progression towards epiphyseal collapse, which in this case did not occur