Your physician needs to do a lot better than "S/P Trauma to the Ankle." That is not a "diagnosis," and he needs to come up with a "real'" and "specific" diagnosis even if it is as mild as a contusion or abrasion, or a severe injury such as a fracture.
As for the External Cause Code(s), yes all the elements of the injury need to be identified, coded, and reported for the Initial Evaluation (except for CMS/Medicare at the moment, and/or depending on the requirements of the patient's insurance company). I refer you to the Website icd10orthocoder.com and check the Coding Blogs, where I have discussed this in detail.
Respectfully submitted, Alan Pechacek, M.D.