Fig. 1

Images of the patient who had pathological fracture of his left patella. A1, A2 Anteroposterior and lateral views showed a well-demarcated, eccentric and osteolytic lesion with pathological fracture of the left patella. B1, B2 CT scan revealed a stage 2 patella lesion (1.5 × 2 × 3 cm) with a thinned cortex, a clear boundary and pathological fracture. Calcifications inside the lesion are shown very well in B2. The lesion did not break through the articular cartilage and did not invade the adjacent femur or tibia. C1, C2 MRI showed that the lesion appeared as slightly intense on T1-weighted images (C1, through the knee in sagittal planes) and intense on T2-weighted images (C2, through the knee in sagittal planes). The soft tissue showed edema at the anterior of the patella. D Whole-body bone scan of the patient. A bone scan showed moderate accumulation of the radiopharmaceutical agent in the left and right patella without strong accumulation in other parts of the body