Henoch-Schonlein Purpura was what the doctors said, but I've since been directed (by another mom who's been through this) to Acute Hemorrhagic Edema of Infancy, which it appears to be.
Mean thing it is.
Her legs Saturday noonish.
The bad news, nothing other than Tylenol and ibuprofen to help her unless the pain is so bad she needs to be hospitalized or get dehydrated and needs to be hospitalized. The joint swelling should be gone in a few days, but the rash will take weeks.
Apparently it is an auto immune reaction she had to whatever virus she had last week.