Maya Animation :: Stretchy Rig And Sharp Bends

So I have set up stretch on my bones and when I stretch it this happens to the skin.

This is how it looks normally: 

What is the most efficient way to do sharp bends on the knees and elbows, He said he used a kneecap joint which rotates around 50% of the knee joint itself using an expression. And with sharp bends on the knees and elbows I mean this.

And then another thing I can't figure out is the foot setup

Here:

Look at how the foot is touching the ground I can't figure out the skinning. this was his bone set up and I did the same thing.