A "chip" fracture, caused no less than by an overextension of one of the tendons connected to the ankle bone, reaching its limit and snapping a piece of bone off! This happened during a bad landing on the trampoline.

He has been 2 weeks "immobilised" in a "slab cast", but today it was removed after another x-ray, as the doctors at the Hospital were happy with the healing so far and their current philosophy with this type of injury to a child of his age is to let them walk on it fairly early on as long as the pain is not unbearable/unmanageable.
Here's to youth and quick healing!