Its all in how you hold the bow.

Try this experiment. Hold you bow arm out as if you are holding an imaginary bow. Chances are you knuckles are vertical (up and down)

Now turn your knuckles so they are horizontal (across).

Notice what happens to your elbow. It turns out.

Try adjusting your grip on the bow so your knuckles are almost horizontal. The only part of your hand that should touch the grip on your bow is the heel of your thumb. Your palm should not make contact with the bows grip.

Shoot with a open /loose grip also!