My Mother had knee surgery on a Tues. She is 73. She did fine after the surgery and the next day she was fine. Napped a lot the second day. She woke on Thurs, the third day, totally out of her head. Nurses said it was sundowners and suggested she might have already had it before the surgery and had hid it in her own home environment. No one at the independent living where she has lived for three years have seen any signs and agree with me, that if it is sundowners, it is related to the surgery. She is also fighting a UTI, which can cause confusion. It is day four and she seems to get worse. She is a big women and I read the meds given during surgery can reside in the fatty tissue, which means maybe someone smaller might get through this in a few days and someone bigger it could take longer? She is seeing things and people who aren t there and experiencing many of the more severe symptoms. And, it isn t going away during the day..it is going on all day and then getting a bit worse at sundown . And she isn t sleeping at night. I don t even know how she is going on the little sleep she has had going on five days now. How long can this last?