Ankle and foot radiographs were done for a young patient with a lateral ankle sprain. Lateral ankle region soft tissue thickening was reported but an avulsion fracture was missed (yes by me).

Ultrasound a week later shows calcaneofibular ligament bony avulsion from the calcaneum, anterior talofibular ligament sprain, or partial thickness defect. With 'perfect hindsight', the fracture was visible in the initial x-ray.

A companian case with MRI: https://doi.org/10.53347/rID-62452