President-elect Joe Biden slipped and fractured bones in his ankle while playing with one of his dogs, his office said Sunday.

In a statement, Kevin O'Connor said Biden has sustained fractures in his mid-foot and will "likely require" a walking boot for several weeks. "Initial x-rays didn't show any obvious fracture, but his clinical test warranted more detailed imaging," CNN quoted O'Connor as saying.

O'Connor is Biden's primary care physician since 2009 and the chief of executive medicine at The George Washington Medical Faculty Associates.

The incident happened Saturday while the 78-year-old Democrat while playing with his German shepherd pet Major, Biden's office said. Major is one of Joe and Jill Biden's two German shepherds. The other is named Champ.

The two dogs will be the first White House pets to be given the title "first dogs." The Bidens have also mentioned they plan to get another pet - a cat.

Reporters covering Biden were not afforded the chance to see him enter the Delaware Orthopaedic Specialists in Newark, Delaware, despite multiple requests.

Biden will be the oldest American president when he is sworn into office on Jan. 20. The 74-year old incumbent Donald Trump has repeatedly tried to portray Biden as feeble and senile because of his age. But Biden has parried such criticisms, saying he is more physically fit than Trump.

Biden's doctor has called the former U.S. vice president as "vigorous" and "healthy" in a 2019 three-page medical summary of his health. 

Biden has a history of health conditions. In the 80s, he suffered two brain aneurysms and was diagnosed with a pulmonary embolism and deep vein thrombosis.