Re: A question for the experienced.
I have just seen this thread and would add my comments as the chief instructor of a general dojo. I tend to ask prospective students if they have any disabilities, or have had any previous injuries, which might impact the level of training in the dojo, where the members rank from total beginners to 4th dan.
I agree with Mary Eastland's and Ross Robertson's comments. If you came to my dojo and had some injury, even a minor injury -- and then I discovered that you had previously had a severe injury, I would want to know why this information had not been given before.
Not so long ago s student enrolled in the dojo. He was doing his PhD and had trained before, but in a Yoshinkan dojo, where he had gained 1st kyuu. He had no injuries and was a good uke, but I had no problem with the Aikikai in promoting him to 1st dan at his next grading. I agree with Ross that rank is like a currency, but where the cash value differs from organization to organization.