I struggled with back pain using Mo's "Head Over The Ball with the Athletic Position" at the start of the approach. So in order to compensate, I stand straight up and open my hips. The first two steps are long and slow, the next two are shorter and quicker and the slide is exactly that..... a slide! This is when I get the deep knee bend and relax my trail leg behind me. Its the most simplistic and tensionless way for me to go to the line. I can bowl all day with no pain in my back or knee.

I utterly cannot believe that you're proceeding with this.

The 2 worst things that you can do, for your own health in bowling is one, not to slide, and two, to keep a stiff or straight knee and not bend it. You can almost guarantee that, sooner or later, you are going to seriously hurt yourself.

Have you even been to a doctor or an orthopedist to learn what is causing the pain?
Have you tried any therapies, physical, chemical or muscular, at all? Have you had X-rays or an MRI?

If your knee already hurts when you bend it, you 're only going to damage another portion of your knee if you keep it straight, instead of bending it like you should.

I would agree with what Jeff is saying though I will point out many of us are 6' and taller and agree that slide is needed for healthy overall knee, leg, hip longevity.  Now for shorter bowler a slightly more upright position may be helpful.  Think Dave Ferraro and Butch Soper who are both shorter and have no knee bend.  These two are the anti-thesis of Parker Bohn III's deep knee bend.

The OP has not stated his overall physical state and height.  Many of us carrying those extra pounds also put a lot of stress on our bodies.   

RE doctors, I know theres something going on down there.. just have to man up and go and see one!!!

Yep. Do yourself a big favor. (Maybe your wife, girlfriend and parents, too?)

You're young enough to lose a lot of years of bowling enjoyment at the least, if you hurt it permanently. It might be something so simple to care of, but you really have to know. Believe me, I've been there. There are things I didn't care of when I should have and I really regret it, both monetarily and pain-wise. Good luck.

Just curious, have you always had knee pain when bowling? Say if you went bowling today it may be fine but if you went again tomorrow it would be sore as soon as you started bowling?

Have your knees checked  by a doctor.