So you are telling me that if an older person joins aikido who has bad knees that they can't test and go up in rank? You can do the same techniques from standing as you can in suwariwaza. In my dojo, a person with bad knees wouldn't even be able to test and would be 6th kyu forever because suwariwaza shomenuchi ikkyo and suwariwaza ryotedori kokyuho is on the first test.
That just doesn't seem fair to me......
Well i guess that would beg the question of why suwari-waza techniques are in the grading if they aren't relevant...
I guess that what i'm saying is that if you can't do a technique (whether that is tenchi-nage or anything in suwari-waza), then it doesn't make sense that you are given a grade which, by definition, says that you can do that technique.
And surely grade is an important thing in this sense: if somebody unable to perform something on the 2nd kyu syllabus was given a dan grade in spite of this, and was to end up teaching a class (which a dan grade permits you to do, in a lot of cases at least) which included this technique, then somebody may get seriously hurt.
The fact is, as 'happysod' said: permanent disabilities or illnesses may affect your capabilities; - we're not all gonna be big sports stars, or astronauts - that's life. It'd be great to give everybody a black belt, and make them feel really good, but you have to do certain things to get it; and if you do give grades out willy-nilly then it will make a mockery of the hard work put in by people who have truly earned them, and you won't be able to tell anything about somebody's proficiency by grade; the point of a grade would be nullified.