Figure 1. (a) Eccentric solid periosteal reaction/cortical thickening, and medullary sclerosis in the proximal tibia. No nidus or fracture line is seen, and there is no focal bone destruction. (b) Coronal short tau inversion recovery MR image. There is medullary oedema and low signal (representing callus), with adjacent cortical irregularity. Oedema is seen adjacent to tibia in muscle and subcutaneous tissues. (c) Sagittal T₁ MRI. Medullary oedema is seen as reduced signal within fatty marrow, and a cortical lesion is seen posteriorly. (d) Axial proton density and (e) T₂ fat-saturated images showing medullary and soft tissue oedema. The cortex is thickened posteriorly, and contains a sagitally-orientated defect, which could be followed on adjacent axial images (arrow). (f) Axial high-resolution CT and (g) sagittal reconstruction. An ill-defined fracture line (arrow) with adjacent periosteal and endosteal callus is seen in the posterior tibia. A longitudinal/sagittal fracture line with surrounding callus is seen on the reconstructed image. Diagnosis: longitudinal tibial fatigue fracture.