PMC5294362_01
CT images on axial (a) and reconstructed coronal (b) plane in soft tissue window reveal a low-density intra-articular mass similar to fat with multiple villi projecting inwards (arrows), which are surrounded by joint fluid with higher density than fat but lower than water. Distention of the joint capsule is evident.
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fig1
No bone erosions were seen (Figure 1).
MR images on coronal T1-weighted (a), sagittal PD-weighted with fat saturation (FS) (b), and axial, sagittal, and coronal T1-weighted with FS after iv administration of gadolinium (c), (d), and (e), respectively, depict frond-like villi projecting inwards from the synovium with signal equal to fat on all imaging sequences (short arrows). After iv administration of gadolinium, enhancement of the overlying synovium is observed (long arrows), but no enhancement of the underlying fat is detected. Joint effusion is present distending the joint capsule, without any sign of menisci or ligaments' injury, or osseous erosions.
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fig2
After intravenous (iv) administration of gadolinium, enhancement of the overlying synovium was observed, with no enhancement of the underlying fat (Figure 2).
Open biopsy (intraoperative view). Incision is part of the final one (a). Biopsy specimen (b).
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fig3
The patient was programmed for biopsy, which confirmed the diagnosis (Figure 3).
Open synovectomy (intraoperative view). Red-black region of synovium is the site of foregone biopsy (arrow).
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fig4
Retropatellar fat pad was debrided as well (Figure 4).
Broad papillary projections lined by synovial membrane. The stroma consists of lobules of mature adipose tissue with focal chronic inflammatory infiltration [Hematoxylin and Eosin stain x100 (a) and x200 magnification (b)].
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fig5
No signs of malignancy were detected (Figure 5).
The patient in the first month postoperatively with his operated knee fully flexed.
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fig6
The patient regained a full range of knee motion from the first postoperative days (Figure 6).
PMC5294362_02
MR images at the same sagittal level on T1-weighted (a), PD-weighted with FS (b), and T1-weighted with FS after iv administration of gadolinium (c) demonstrate medial compartment osteoarthritis with marginal osteophytes, chondral lesions, subchondral changes, and a complex tear of the posterior horn of medial meniscus. Mild villous frond-like fatty subsynovial hyperplasia is present in the suprapatellar bursa associated with synovial proliferation, which is enhanced after iv administration of gadolinium, and joint effusion (arrows). MR images at the same axial level on T1-weighted (d), PD-weighted with FS (e), and T1-weighted with FS after iv administration of gadolinium (f) confirm the above findings (arrows), which are strongly suggestive of LA.
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fig7
These findings were suggestive of LA (Figure 7).
PMC5294362_03
Tc-99m scintigraphy demonstrates persistent concentration of the technetium in the right knee joint, which is indicative of an inflammatory process.
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fig8
No radionuclide concentration was depicted on the left knee (Figure 8).
US examination of the right knee on axial (a) and longitudinal (b) sonograms reveals hyperechoic frond-like projections of the synovium into the effusion (arrows), findings suggestive of LA. Colour Doppler US (c) does not depict any blood flow in the affected area.
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fig9
MR images on sagittal T1-weighted (a) and PD-weighted with FS (b), on coronal T1-weighted (c) and PD-weighted with FS (d), and on axial STIR (e) and T2-weighted (f) demonstrate synovial proliferation and a large primarily fat-signal mass on all MR sequences, filling much of the suprapatellar bursa with a frond-like appearance, which is surrounded by excessive joint fluid. The innumerable individual villi are small in this case, with small quantities of interposed fluid, creating a feathery appearance (arrows). These findings are indicative of a large feathery-appearing LA filling the suprapatellar recess.
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fig10
These findings were strongly suggestive of LA (Figure 10).