I don't know, depends what they see or don't see on the x-ray
CT scan if it's bone they want to examine, MRI for strings and soft tissue
based solely on my one experience
I had an x-ray at minor injuries, they looked at it and decided that my smashed bone (one big piece of talus not where it should be) couldn't be a new injury and sent me away to walk on it
a few days later, someone who knew a bit more about stuff reviewed the x-ray, phoned me up and booked me in for a CT scan - which revealed the true devastation (talus in a dozen pieces)