Chicken pulley cannot stand

[drdanags]

All was well with her this morning. When I went out she was lying in a spot she dug out in the dirt, unable to stand. No obvious injury. Can move her right leg and tilts head that way. her left side, around her ear area is red not sure if it is from lying on that side. Can move left leg, when I gently extend it, but draws it back up again. Lays down on left side and cannot right herself and doesn't really try to get up much. What is this? HELP