short and long pasterns

Question
hello sir, may i know why "short" and "long" pasterns are considered to be faulty confirmation in horses? can you explain me in detail?

Answer
HI     A HORSE HAS A SHORT AND LONG PASTERN.  THE SHORT PASTERN IS INSIDE OF THE FOOT AND MAKES THE FIRST JOINT IN THE FETLOCK. THE LONG PASTERN CONNECTS TO THE SHORT PASTERN AND SHOWS UP JUST ABOVE THE PASTERN JOINT AND IT ALSO GOES UP TO THE ANKLE JOINT. PLEASE LOOK AT YOUR HORSES ANKLE AND FEEL AS YOU GO DOWN FROM THE ANKLE TO THE FIRST JOINT. YOU WILL FEEL THEN YOU WILL FEEL THE TOP OF THE HOOF.  THANKS  ED HESS