"I have a tear in my left calf so it's very painful to even walk," she told reporters.
"I got it after my second match so I just aggravated during this match. Today was just a sharp pain, a bit too much, I couldn't really move on the court."
Stosur also created some history for her country by becoming the first Australian woman into a grand slam final since Wendy Turnbull in 1980.
She needed just one hour to thrash fourth seed Jankovic.
Stosur, who put out four-times champion Justine Henin and world number one Serena Williams en route to the last four, sauntered to a comprehensive victory on Court Philippe Chatrier under clear blue sky and warm sunshine.
In a courtside interview, the Aussie declared herself ready to lift the famous trophy.
"Yeah, I think so. Why not?! Saturday will be no better day than any other one," she said.
"I've been playing well and I'm just looking forward to getting into it. If I can keep this form going, I think I've got a good shot."