Pain medial ankle.

There's oedema in the deep deltoid ligament fibres, associated with mild thickening of the anterior talofibular ligament. Nodular thickening on the articular surface of the ATFL is suggestive of a meniscoid lesion. The appearance is typical for a lot of ankle inversion injuries.

The patient "rolls" his ankle. The medial aspect of the talus abuts the distal tibia, and the lateral side is stretched. This results in anterior talofibular ligament tear, and fluid in the anterolateral gutter.