A healthy 65-year-old female was admitted to the emergency department complaining of acute pain at the lateral aspect of the knee. She had no history of trauma or rheumatological disorders. Radiographs of the knee were performed (Fig. 1), and non-steroidal anti-inflammatory medications (NSAID) were administered. After eight days of symptomatic relief, she was referred suffering acute pain, again at the same site. An MRI scan was then obtained for further investigation (Fig. 2).

Fig. 1
figure 1

a Anteroposterior plain radiograph of the knee obtained at the emergency department; b enlarged detail of femural cortex and calcifying lesion

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Fig. 2
figure 2

MRI scan acquired eight days after initial onset of symptoms: a STIR weighted image (TR/TE/TI:3600/20/90) coronal view; b MRI T2-weighted image (TE = 100; TR = 5100) axial view

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