PMC5298408_01
MRI at presentation, three weeks after symptom onset. (a) Coronal STIR and (b) coronal T1W images. There was bone marrow edema mostly in the medial half of the medial femoral condyle, otherwise milder and more diffuse in the rest of the condyle, with an appearance more suggestive of contusion than of osteonecrosis. No specific trauma preceded the symptoms, however, the patient had been walking a lot on hard surfaces three weeks earlier.
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MRI showed non-specific bone marrow edema (Fig. 1).
MRI three weeks after presentation. (a) Coronal STIR and (b) coronal T1W images. Increase of bone marrow edema both in intensity and extension, with the edema on sagittal images (not shown) now centered around the weight bearing area of the medial femoral condyle, suggestive of osteonecrosis.
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At follow-up MRI after three weeks (Fig. 2) the bone marrow edema had increased both in intensity and extension, and was suggestive of osteonecrosis.
MRI at three months. (a) Coronal STIR, (b) coronal T1W, (c) sagittal PD-weighted images. Further progression of signal intensity of the bone marrow edema on a STIR sequence with stable distribution. On the sagittal T1W images a double sclerotic line (arrow) could be seen in the subchondral weight-bearing area.
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MRI at three months showed unaltered distribution but further progression of signal intensity of the bone marrow edema (Fig. 3).
MRI at five months. (a) Coronal STIR and (b) coronal T1W images. Subtotal regression of the bone marrow edema on coronal STIR images. The subchondral double line was still present on sagittal T1W images (not shown), and a small cystic area with minimal impression and flattening of the joint surface on the weight-bearing area of the medial femoral condyle had appeared (arrows). The findings were now interpreted as osteonecrosis.
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At five months, MRI showed subtotal regression of the bone marrow edema (Fig. 4).
MRI at seven months. (a) Coronal STIR and (b) coronal T1W images. Slight progression of the subchondral cystic area and reappearance of a discrete bone marrow edema.
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MRI at seven months (Fig. 5) showed slight progression of the subchondral cystic area and reappearance of a discrete bone marrow edema.
MRI at ten months. (a) Coronal STIR and (b) coronal T1W images. Further slight progression of bone marrow edema, with filling out of the cyst, discernible on T1W images.
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At ten months, MRI showed further slight progression of the bone marrow edema, but with filling out of the cyst (Fig. 6).
Radiography at one year and three months. Minimal subchondral lucency with preserved joint congruency and joint space width.
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At one year and three months a minimal subchondral lucency had appeared at radiography (Fig. 7), while MRI (Fig. 8) showed further healing of the cyst.
MRI at one year and nine months. (a) Coronal fat-suppressed PD-weighted and (b) coronal T1W images. Minimal remaining subchondral edema on fat-suppressed PD-weighted images with mildly irregular trabecular structure at the location of the former cyst.
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At one year and nine months, MRI showed minimal remaining subchondral edema (Fig. 9).
MRI at two years and six months. (a) Coronal fat-suppressed PD-weighted and (b) coronal T1W images. Further healing on fat-suppressed PD-weighted images with disappearance of bone marrow edema with remaining small subchondral irregularities, preserved joint surfaces and cartilage.
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The final MRI at two years and six months (Fig. 10) showed further healing, also at radiography.