THE HANDS - In doing complex bending of joints, the approach is to try the samples below. You can also look at your own hands and copy them:
THE FEET - It is interesting how a horseshoe resembles the extreme front view of a human foot. See below. Just visualize it facing you.
It could go back to doing the stick figure:
When I was a kid, my first drawings were sticks. Sounds too elementary? Not at all. A good technique in figure drawing is to do it like when you are a kid. Do the stick figure.
It is like a skeleton dressed up by muscles. The only difference is, you should now do it with a sense of proportion. By applying this technique, your drawing will be easier to project. Complex postures and actions get done using sticks.