An anonymous commentor has given me correction
There is more to Kosher beef than just draining the blood. But it would be a doctoral dissertation to list all the requirements and the variations on them (removing the fat, purging nerves, etc) and when I rant I just want to rant.
The sciatic nerve (along with the fat) must be removed from the hind quarter to be considered kosher.
The removal of Chelev and the Gid Ha'Na'sheh - known as Nikkur in Hebrew ("Treiboring" in Yiddish, derived from the Czech) - is complicated and tedious, and special training is required to be able to do it properly. Since the Gid Ha'Na'sheh and most of the Chelev is found only in the hind quarters of the animal, the custom developed in most Jewish communities outside of Israel to eat only meat from the front of the animal, thereby avoiding the concerns of ensuring that all forbidden fats and nerves in the hindquarter are properly removed. Such an arrangement is feasible in countries where a large non-Kosher market exists, especially since the non-Kosher market considers meat from the hindquarter as more tender and desirable. It is interesting to note that Rabbi Yaakov Yosef zt"l, the first (and last) Chief Rabbi of New York City, instituted this custom in the United States in the late 1800's. Many of Rabbi Yosef's efforts to improve the standards of Kashrus in the New World were resisted by the established "Kosher" meat market, and went unappreciated in his lifetime. Indeed, the aggravation and calumny to which he was subjected brought him to an early death. His lasting achievement in this field, however, was the successful promulgation of the policy to avoid the use of the hindquarter, thus ensuring that issues of Gid Ha'Na'sheh and most of the Chelev in the animal would not pose a significant concern to the Kosher-observant community.
I did not know that this particular practice was uniquely "American", but it makes sense as any complicated meat cutting that has to be done by hand will raise the price of the finished cut of meat.
But while this is a good point, my original point still stands, that if the preparation of the animal is kosher, then the meat is kosher. So if you want a kosher leg roast you'd better get to know a a kosher butcher.