when you slow it down, everyone goes into rotation before the stride foot hits the ground. your stride foot is slightly closed at landing but not completely. that locks up any rotation and would really stress the knee.
you develop force one of three ways. horizontally in a straight line from the ball of the rear foot to the ball of the front foot toward the plate. rotationally- rotating the hips first and lagging the shoulders behind (separation) to activate the stretch reflex in the large core muscles of the trunk using centrifugal force (very powerful plane). and finally up and down in a predominantly verticle plane pulling down if you throw above the shoulder, and pulling up if you throw below the shoulder by taking the weight and momentum of the upper body toward the plate and transfering the force through the shoulder, elbow hand and the ball (the three weakest links in the chain and how you get velocity off the ball in the change up).
that's pretty much it. everyone uses these planes to different degrees and you have to find one that is safe and works for you, then repeat it until you develop the feel to throw the ball where you want it to go safely.
also need to read the abstract to doc andrews' article in the american journal of sports medicine about risk factors in adolescent baseball pitchers. he is the surgeon who does all the tommy john procedures at birmingham sports medicine institute.
he says the primary factors for blowing out are overuse, fatigue and increased pitch velocity. these factors are greater than pitch type, private instruction, strength and conditioning and pitching mechanics. kind of throws some cold water on us guys that think mechanics and strength training is the cure all for injury prevention. i'm going to order the complete article, but the abstract is free and very good.