Only the forequarter of a Kosher slaughtered animal is brought to Kosher butcheries. The hindquarters are not brought into Kosher butcheries. In Genesis (32:25-33) the Torah recounts the fight that Jacob had with an angel who dislocated his sciatic nerve. Because of that injury we are instructed that the Jewish people do not eat the part of a Kosher animal that contains the sciatic nerve. [source: www.uos.co.za/kashrut/defaultFull.asp]