2,562. A Missing Leg; A Broken Bone
Hilchos Shechita 8:11
An animal that was missing a hind leg since its creation is a treifa; the same is true if it has an extra hind leg, because having an extra limb or organ is the same halacha as one that’s missing. However, if an animal has three front legs, or only one front leg, it is permitted. Therefore, if a front leg is cut off, the animal remains permitted. If a hind leg is cut off from the joint and up, the animal is a treifa; from the joint down, it is permitted. This refers to the joint at the end of the hip, near the body.
Hilchos Shechita 8:12
If the animal’s thigh bone is broken above the joint, or if the whole thing or its greater part sticks out, it’s the same as if the leg was cut and fell off, with the result that the animal is a treifa. If flesh or skin covers both the greater part of the broken bone’s thickness and the greater part of its circumference, the animal remains permitted. This is so even if part of the bone fell off and is no longer there. Soft sinew is not the equivalent of flesh.