The actress known to millions as the tipsy Karen was visibly limping during Sunday night's Emmy Awards broadcast and needed help getting on stage to sing the TV theme from "Green Acres" with Donald Trump.
Mullally told the World Entertainment News Network she decided to seek medical treatment Monday.
"I called my doctor," Mullally said. "She said, 'Go to the emergency room.' So I go and we waited around and I went in and they go, 'Oh yeah, you hurt your foot, you have to go to the doctor.'"
Mullally said she hurt herself while watching TV at home Saturday night.
"There was a stupid commercial with silly music and I was sort of cavorting," she said. "I was doing silly dancing and I went up in the air, came down and couldn't walk. I think I tore a muscle in my calf, apparently, so we'll see."