US President-elect Joe Biden twists ankle playing with his dog

US President-elect Joe Biden has suffered a nasty ankle injury after slipping while playing with his dog Major, his office has revealed.

The 78-year-old, who is set to become US President in January 2021, had his ankle examined by a doctor out of "an abundance of caution" after the injury on Saturday (local time).

Initial x-rays on Sunday showed there was no obvious fracture, but a follow-up scan indicated he'd suffered hairline fractures to his lateral and intermediate cuneiform bones.

It is anticipated Biden will require a walking boot for several weeks as he recovers, his physician Kevin O'Connor said in a statement.

Major, a German shepherd rescued from the Delaware Humane Association in 2018, is set to make history in January by becoming the first rescue dog to grace the halls of the White House.

He's one of two German shepherds the Bidens own, the other named Champ. It's understood Biden has a soft spot for the breed, having owned and trained them since his childhood.

The Bidens say they will bring both their dogs to the White House, and also plan on getting a cat.

The last four years under Donald Trump marked the first time in US history that a President did not have dogs in the White House.

The Trump family had no pets at all - likely because the outgoing President reportedly dislikes them. In her 2017 memoir Raising Trump, the real estate mogul's first wife Ivana claimed "Donald was not a dog fan".

An Instagram post shared by Biden just before Election Day came with a simple campaign message - "let's put a dog back in the White House!" - alongside a video compilation of dogs sporting different campaign paraphernalia.