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Oblique Left Foot Radiograph Demonstrates a Fragmented Os Peroneus. (A) Oblique left foot radiograph demonstrates a fragmented os peroneus (arrows) with 12 mm distraction of a proximal fracture fragment to the level of the peroneal tubercle, a curved prominence on the lateral aspect of the calcaneus (arrowheads). A peroneal tendon injury is suggested with distraction of os peroneus fracture fragments greater than 6 mm, or with migration of an os peroneus proximal to the peroneal tubercle. A subsequent foot MRI of this patient demonstrated a complete peroneal tendon tear with proximal retraction of tendon fibers. (B) Radiographs of the same patient 7 years prior demonstrate an intact os peroneus distal to the peroneal tubercle (arrow). Contributed by D Byerly, MD