High profile toilets?

I am shopping for a new toilet (actually two). I want them to be "high profile" (i.e. ADA compliant.) The specs on most show 16 1/2" to rim for high toilets, confirming what my local plumbing showroom salesperson told me--that this is the industry standard. I did find a Kohler that shows a 17" height in the specs. The TOTO Drake CST744SL states something about meeting ADA requirements "where installed so top of seat is 17" - 19" from finished floor."

So what gives? When testing the 16 1/2" toilets they still don't seem very comfortable for someone with long legs and very bad knees. I swear I have been on higher toilets at others' homes or in stores. restaurants, etc. Is installation that will raise toilet rim height unusual or difficult? HELP.

I installed a American Standard Circa 1922 toilet for a chiropractor about 4 months ago. The guy actually is built like Arnold Sch. and threw the toilet on his shoulders and took it up the steps like it was nothing. I believe that is the tallest toilet I have ever installed, let alone the largest. It stood tall and looked like an almighty porcelain throne. I personally like Toto toilets the best. They make seat extenders in your situation, also grab bars that make getting on and off any toilet easy. I don't have bad knees but I am sure it is difficult in your situation. If you have an adjoining wall close to this toilet I would suggest a large grab bar to help yourself on and off the toilet as well.