It took my internalizing and consulting with my instructors to understand the knee pain I had was the result of leaving my foot in place while the knee started the turn. The knee can't be ahead of the foot (torquing the knee), the knee and the foot turn as one. This is my current understanding... and my knees don't hurt anymore!
As far as up and down, I've been taught to turn without raising the hips (still working on it - 1st kyu here). You give something back to uke you (should) have taken earlier. I suppose that doesn't preclude the foot itself moving up and down with the knee absorbing the up and down to keep the hips from bobbing.
To Graham, as to my other comment on "forward" I meant the intent of the turn shouldn't ever be backwards. Same with pivots.
Working through this myself... not preaching
Thanks. Of course you're not preaching, we are merely communicating.
Yes, attention on going forward and never backwards I understand and is indeed to be understood and practiced and as usual lead you to various realizations and accomplishments and improvements. That's all good.
As a circle or turn or energy can go clockwise or anti clockwise or along any number of paths and directions then eventually we would then learn to turn backwards just as comfortably as forwards talking physically but if you then look again and notice that we are aware of and moving with and even leading then the physical direction whether physically forwards or backwards to us is always forwards.
As far as no up and down goes then I know we are on the same page. Once again the words may get in the way for some and thus the misunderstanding.
Funny you mention knees. Here's an interesting point and it's to do with knees and turning both.
In my experience I have found many, especially non Japanese have problems doing techniques from the knees ie: suwariwaza, kokyudosa etc. "Ah, my knees hurt or I've got bad knees through doing that or too much of that or........"
Anyway, I give them a cure for it and voila no problem with the knees. It all boils down to turning correctly. Turning incorrectly gives them bad knees. Notice in this example I give here there are no feet supporting you and the knees have now become the 'feet'. Thus there is also a major lesson to learn from doing all moves from the knees in good fluid flowing effective motion and that is that the turning has very little in essence to do with the feet.
Continuous taisabakis from kneeling is where this is learned but if not done properly merely leads to damaged knees and the thereafter focus and debates on knees this kness that and knees the other and all kinds of added on theories all because the essence and principle was missed in the first place.
A bit like feet debates really I would say.