Joe Biden has slipped and twisted his ankle while playing with his dog Major in Delaware, his office have confirmed.
The 78-year-old president-elect was being examined by an orthopedist on Sunday “out of an abundance of caution”.
The accident happened on Saturday, his spokesman said.
Mr Biden is considered fit and active for his age, regularly cycling around his Delaware home and taking care to stay in shape.
In December his doctor, Kevin O’Connor of The George Washington University, released a three-page medical summary of Mr Biden's health at the request of his patient, in which he described Mr Biden as a “healthy, vigorous, 77-year-old male, who is fit to successfully execute the duties of the Presidency to include those as Chief Executive, Head of State and Commander in Chief.”
He had emergency surgery for two brain aneurysms in 1988, but made a full recovery.
Mr Biden, like Mr Trump, has not publicly released his medical records during this campaign.
The Bidens have two German shepherds - Major, two, and 12-year-old Champ.
Major was adopted from a shelter, and will be the first rescue dog to live in the White House.
Champ was purchased from a breeder in Pennsylvania.
The tradition of presidential pet ownership dates back to George Washington and has been carried on by 30 of the 45 presidents.
Mr Trump was the first president in more than a century without a pet — a fact seized on by his critics.
In 2002, George W. Bush cast his Scottish terrier Barney as the star of what would become an annual White House Christmas video.
The Obamas’ Portuguese water dog Bo featured prominently in his second campaign.
Mr Trump, who is believed to have never had a pet, was dismissive of the idea that he should change the habit of a lifetime.
“How would I look walking a dog on the White House lawn?” he told a rally in El Paso in 2019.