right knee in downswing

A question i have been wondering is about the right leg and knee. In the downswing should the right knee stay flexed, looking at my swing my right knee locks up in the downswing i am thinking this is whats causing me to lose posture and stand up at impact any one got any drills, swing thoughts or ideas on how to maintain flex in the right knee during downswing if that is indeed what you are supposed to do thanks all for advice appreciated as usual this forum has many knowledgeable members to many to list

There are a number of things that could cause the right knee to straighten during the downswing:
A reverse weight shift, having the hips turn incorrectly (or too much) on the backswing, having the knees too bent at address with the hips set low and back (with weight on the heels).

A good drill and feeling to get is to setup and hold a club shaft against the top of your thighs (like a weight lifter with a barbell). Apply pressure downward on the top of the thighs with the shaft while feeling the thighs pushing back upwards (keep your hips high you don't want to feel like you are sitting down). Then when you swing try to feel like you maintain that pressure on the thighs which should keep your knee flex maintained. That in turn should help with your posture, power storage, maintain your swing path, and keep your hips from spinning out on the downswing.

Yeah, undoubtedly the right knee stays flexed (never straightened) throughout the swing. But what puzzles me is that some say that driving the knee forward on the downswing adds power. I find that to be quite a difficult athletic move... Is it true?

Take a wider stance and flex the knees a little more at address. If you a have a narrow stance its almost impossible to keep the right knee from straightening without swaying

As you then turn back try feeling like your left knee doesnt collapse - like to stays facing the target thus keeping the space between your knees

Sorry but I gotta disagree... the left knee should collapse on the backswing on most shots... At times (for special shots) you may keep the lower body quiet but that is the exception... Any other opinions regarding this?

Perhaps we arent agreeing on what we mean by collapse but have a look at these articles

http://www.improve-your-golf-swing.c...olf-swing.html
http://golfergalaxy.com/Golf-Instruc...-the-Ball.html

The left knee should turn in slghtly as you turn but it shouldnt completely collapse towards the right knee. My brother in law has been struggling with this in his backswing and it causes him to sway and hit some weak pulls

Yes, the left knee should turn in. Perhaps collapse is not the right word after all. Certainly any swaying should be avoided.

No driving the knee does not add power. That was a common swing thought in the 70's and Greg Norman, Nick Faldo, and Nick Price were players who found themselves doing that and had to work hard rid themselves of that bad habbit when they moved to more modern consistent swings.

Look at the pictures of Trevor Immelman (who is longer than the average PGA Tour player in driving distance). His right knee isn't driving, and instead it is pulled into the downswing. His right foot is still low to the ground at impact like most good players.
http://www.golftoday.co.uk/proshop/f..._reaction.html

Another example is Fred Couples who is currently 7th in driving distance on the PGA Tour. Looking at pictures of Couples it is clear that the hips make the large move in the downswing, and the legs are pulled along:
http://www.earthgolf.com/fred/news-info/swing-analysis/

I just cant get the idea or feel of how the hips should work in downswing no matter what i try or feel when i look on video my right hip is riding high destroying my spine angle and causing the right knee to lock up maybe i have been playing too long with this swing fault and its impossible for me to fix realy frustrated i would love to hit one shot without losing my posture

No swing fault is impossible to fix.
My guess is that you problem is either caused by the way you setup to the ball, or a bad position you get into during your backswing. If you have a picture of you at setup and/or the top of the swing or a video of your swing you could link then someone with a fresh pair of eyes (who isn't you ) might be able to notice something you may have missed.