A clear X-ray, or a clinician bringing up an MRI, leaves a simple question about what the second scan adds. The two scans look at different things, and that difference is the answer.
What an MRI shows
A detailed look at tendon and other soft tissue is what an MRI offers, and a clear X-ray does not settle every ankle question. NIH PMC describes MRI as a valuable imaging modality that provides detailed visualization of bone, joint, tendon, and other soft tissue abnormalities. RadiologyInfo.org states that some chronic ankle conditions cannot be seen on x-ray.
Read about each test first
You do not need training to look up what a scan involves. MedlinePlus explains the leg MRI scan and the joint x-ray, and RadiologyInfo.org covers musculoskeletal ultrasound. Reading ahead costs nothing and commits you to nothing.
When to ask a professional
Which scan fits your injury is a call for the clinician who examines you, in Wood Dale or anywhere else. If pain keeps going after a normal X-ray, ask whether further imaging makes sense for your case.
A note for first-timers
Nobody expects you to know the tests in advance. Knowing the names of the three scans above is enough to ask good questions at your next visit.