"Clarke's very poorly but he's alive and stable. Best Christmas gift we as a family could ask for. Thanks again," she told well-wishers.
In her previous tweet, Gemma wrote, "Don't normally use this account anymore. But have been overwhelmed with your thoughts and prayers. Thank you."
Clarke, 35, was airlifted to Leeds General Infirmary on Monday after the accident, which took place near Bishopthorpe at 7.30am.
A North Yorkshire Police spokesperson confirmed: "The collision involved a male pedestrian and a lorry. The injured man has been airlifted to Leeds General Infirmary with serious injuries.
"The road was closed to allow the air ambulance to land and to allow collision investigators to examine the scene."
Clarke's very poorly but he's alive and stable. Best Christmas gift we as a family could wish for. Thanks again.— MrsC (@gemmacarlisle) December 23, 2014
Following the news, the world of football has pledged its support and best wishes to Clarke, a former Professional Footballers' Association chairman, and his loved ones.
"Everyone is keeping Clarke in their prayers and thoughts," a statement from the PFA read. "We are offering our full help and support to him and his family."
The PFA's sentiments were echoed by a number of Clarke's former clubs, including Burnley and QPR, and former Downing Street communications chief Alistair Campbell, a Burnley fan.
"Really hoping @clarkecarlisle going to be ok. Thoughts with Gemma/two lovely kids. A great @BurnleyOfficial man and mental health campaigner," he wrote.
Clarke made more than 500 appearances for nine clubs during his 16 year career. He is also considered one of the most intelligent footballers of his generation; in 2002 he was awarded the title 'Britain's Brainiest Footballer' by BBC Sport, and was the first player to appear on both Countdown and debate show Question Time.
He is also a leading ambassador for anti-discrimination group Kick It Out, who tweeted on Monday evening, "Stay strong our dear friend – keep on fighting."