PMC4799239_01
Frontal (a) and lateral (b) radiographs of both knees demonstrate a lytic and round lesion with well-defined margins in the subchondral regions of the superolateral quadrant of both patellae (arrows)
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Fig1
Radiographs of both knees showed a lytic and round lesion with well-defined margins in the subchondral regions of the superolateral quadrant of both patellae, in keeping with bilateral dorsal patellar defects (Fig. 1).
Frontal (a) and lateral (b) radiographs of both knees that were made 9.5 years earlier show no abnormalities
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Fig2
Interestingly, radiographs of both knees that were made because of chronic knee pain 9.5 years earlier, at the age of 6.5 years, showed no abnormalities (Fig. 2).
MRI of the right knee (a-e) and left knee (f-j) with sagittal proton-density (a, f), sagittal T2-weighted spectral attenuated inversion recovery (b, g), sagittal 3D water selective fluid (c, h), coronal proton-density (d, i), and magnified axial proton-density (e, j) slices shown. The lesion in the superolateral quadrant of both patellae, consistent with dorsal patellar defect, is demonstrated (arrows). Note the associated cartilage involvement with a slit-like defect/apparent discontuinity on both retropatellar surfaces (e, j, arrowheads). Also note the widespread surrounding high T2 signal in both patellae, consistent with bone marrow edema (b, g). MRI did not show any other abnormalities in either knee
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Fig3
MRI not only demonstrated the bilateral dorsal patellar defects, but also showed an associated deep slit-like cartilage defect with widespread surrounding bone marrow edema in both patellae (Fig. 3).
Eight-month follow-up frontal (a) and lateral (b) radiographs of both knees still demonstrate the dorsal patellar defects (arrows), without any obvious changes compared to 8 months earlier (Fig. 1). However, the patient was almost symptom-free at the time of this radiographic examination
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Fig4
Radiographs of both knees still showed the dorsal patellar defects, without any obvious changes compared to 8 months earlier (Fig. 4).
Eight-month follow-up MRI of the right knee (a-d) and left knee (e-h) with sagittal proton-density (a, e), sagittal T2-weighted spectral attenuated inversion recovery (b, f), oronal proton-density slices (c, g), and magnified axial proton-density views of the patellae (d, h) shown. The dorsal patellar defects are still present, but the surrounding bone marrow edema has decreased considerably (b, f) compared to 8 months earlier (Fig. 3). Only in the left knee some noteworthy bone marrow edema is still seen (f, arrowhead). Also note progressive "filling" of the dorsal defects with apparent (onset of) "closure" of the slit-like defects/discontuinities on both retropatellar surfaces (d, h, arrowheads) compared to 8 months earlier (Fig. 3). The patient was almost symptom-free at the time of this MRI examination
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Fig5
However, MRI of both knees showed a considerable decrease in the amount of surrounding bone marrow edema compared to 8 months earlier (Fig. 5). In addition, MRI showed progressive "filling" of the dorsal patellar defects with apparent (onset of) "closure" of the slit-like defects/discontuinities on both retropatellar surfaces compared to 8 months earlier (Fig. 5).