We have a hen here who I think broke her leg at the knee. Honestly, the other chickens are not picking on her so I left her go without taking her away from the others. She was hopping, putting no pressure on the leg, and couldn't use it at all. Week and a half later she is now getting around A LOT better, her "good leg" has gotten stronger, and she is putting some pressure on the bad leg. No one picks on her. She tends to stay inside the barn where she is safe from predators, but will hop over to the doorway to sun bathe. When everyone is put up, she'll just head over to them and they'll just pile together.
We chose not to separate as for us we wanted her to continue to use the good leg to gain strength, and she was still eating/drinking as normal--and most importantly none of the others were harassing or hurting her. This worked for her, and for us--it may not work for you. If the others were going after her, she'd have been isolated.
