About a month ago one of our hens (year old) started limping. Wife and I went out and gave her a thorough going over and couldn't find anything wrong with her, so we decided to keep an eye on her and see if it was some minor injury that might go away (a chicken sprain). There was no sign of anything wrong with her feet, no sign of injury in her legs and her legs moved freely and didn't seem to bother her when we manipulated them. Wife even checked egg vent for any sign of stuck egg. We couldn't find a thing wrong. It only lasted for about three days and then she was back to her perky chicken self. This week (about three weeks after the first incident) she's not only back to limping, she's positively hobbling along, and spends most of the day sitting in a protected spot by the coop. She can't even get back into the coop by herself and can't get on the roosts with the rest of the hens. And once again there are no signs of any injury. Anybody have any ideas of what could be causing this? Wife and I are out of ideas fro things to look for. Other than the hobble she's a magnificently healthy looking chicken!