Localized Pigmented Villonodular Synovitis of the Hip: Sudden-Onset Pain Caused by Torsion of the Tumor Pedicle

Figure 1

(a) An initial anterior radiograph shows no significant findings. (b, c) Enhanced stress radiographs reveal a mobile intra-articular mass. (d–f) Magnetic resonance images: (d) a coronal T₁-weighted image shows a low-intensity mass lesion located inferior to the hip joint; (e) a coronal short τ inversion recovery sequence shows a mass with both low- and high-intensity areas; (f) a coronal enhanced T₁-weighted image shows marginal enhancement of the mass. (g) Computed tomography image shows erosive changes on the fossa acetabuli and enthesis of the ligamentum teres of the femur.

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