A traditional rotating intern year, if you do one, is the first year out of med school. It is very much like rotations (clerkships) from your third and fourth years of med school. The difference is that you are actually a doctor so you have more responsibility. It used to be the norm in the allo world and it has continued in the osteo world. Now most ACGME (MD) residencies have it "built in" to the first year of your residency (which is called a "categorical" residency). In these residencies on paper you still have an intern year, but in reality it is a seamless transition into your residency.
In the DO world it continues to be a required part of AOA training. You can either do a transitional year or a linked AOA residency that has it built into the first year. The thing is, as a DO you don't have to do AOA training to practice medicine in 45 of the 50 states. You can do an ACGME categorical and totally skip the traditional rotating transitional internship and just not be part of the AOA.
The important exception to this is that you can petition the AOA to have your first year of your ACGME residency count as your AOA transitional year. Then you are still part of the AOA and therefore able to practice in all 50 states without having actually done an AOA approved traditional year.
I hope that made sense. 😉
