case_images: PMC10578391_01
case_images: Patient and comparison normal knee images. (A) Coronal T1-weighted (left) and fat-suppressed T2-weighted coronal (center) and sagittal (right) magnetic resonance images of the right knee. The T1-weighted coronal image shows abnormal, decreased signal intensity in the distal femur and proximal tibia representing osteonecrosis, extending down to the subchondral bone of the femoral condyles at the knee. The dark, serpentine margins on the T1-weighted image (arrows) represent the edges of the infarcts. The coronal and sagittal T2-weight images show white bands of increased T2 signal intensity (arrows) paralleling the margins of the infarcts demonstrated on the T1-weighted images, the "double line sign." The bands of increased T2-weighted signal intensity represent granulation tissue and viable bone. (B) Coronal T1-weighted (left) and sagittal STIR (right) magnetic resonance images of a normal knee show homogenous marrow signal intensity. On the T1-weighted image, the marrow signal intensity is bright (black **) and comparable to that of subcutaneous fat (black *). On the STIR image, the signal intensity from the bone marrow is depressed (white **), again comparable to subcutaneous fat (white *).. Abbreviations: STIR, short tau inversion recovery.
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case_images: Follow-up magnetic resonance imaging (MRI) revealed an extensive serpentine rim of peripheral T1 hypointensity and T2/short tau inversion recovery hyperintensity encompassing the same area, which confirmed intramedullary bone infarcts consistent with osteonecrosis (Fig. 1, with normal comparison).
case_images: Gadolinium contrast images. Fat-suppressed T1-weighted sagittal (left) and transverse (right) images obtained after the administration of intravenous gadolinium contrast. White, serpentine bands of increased signal intensity (arrows) represent hyperemic and viable bands of granulation tissue and correspond to similar bands of increased signal intensity on the fat-suppressed T2-weighted images.
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case_images: Gadolinium contrast images showed areas of increased T2 which reflect the presence of water in tissue (Fig. 2), also referred to as short tau inversion recovery or STIR.
case_images: Bone scan total body assessment. A radionuclide Tc-99 m methylene diphosphonate bone scan shows prominent increased osseous remodeling in the distal femora, proximal tibiae, left proximal humerus, distal tibiae, and right talus representing foci of osteonecrosis.
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case_images: This revealed radiotracer uptake within the left humeral head, distal femora, right greater than left proximal tibia, and right greater than left ankle and hindfoot (Fig. 3).