Quote ="Jake the Peg"Never seen anyone deliberately bending another player's arm back then pumping it up and down in an obvious attempt to cause injury'"
That's a very, very rare occurrence and, again, was 'invented' many, many years ago in wrestling/martial arts. And it doesn't involve 'pumping it up and down', it involves bending the arm back whilst putting pressure on the shoulder and/or elbow. That's something that's happened in the game, accidentally or otherwise, for many years.